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Idaho · Treasure Valley · Pacific Northwest · #115 Most Populous County in the US
Ada County, Idaho
Home to Boise - Idaho's capital city and one of America's fastest-growing metros. Ada County added over 10,000 new residents in 2025 alone. Property tax, courts, public records, probate, and senior services for Ada County residents.
County SeatBoise
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Office: Ada County Sheriff’s Office – 7200 Barrister Drive, Boise, ID 83704 | (208) 577-3306; Sheriff appointed July 2021 and elected in 2022. Idaho’s largest local law enforcement agency, with almost 900 employees including roughly 450 sworn deputies. Deputies patrol unincorporated Ada County and the cities of Eagle, Kuna, and Star. Manages the 1,224-bed Ada County Jail and runs the county-wide 911 emergency dispatch center. Sign up for emergency alerts via “Ada Alert.”
Notes: For an active emergency, call 911. Ada County’s very first sheriff, David C. Updyke, elected in early 1865, is a genuinely dramatic figure in the county’s history – he was later revealed to have used the office as part of an organized crime ring with ties to Montana’s notorious Henry Plummer, a documented and notorious episode referenced here factually.
Roads & Utilities
ROADS & TRANSPORTATION
Roads: I-84 and I-184 serve Boise, the county seat and largest city, Idaho’s state capital.
Notes: Ada County was created by the Idaho Territory legislature on December 22, 1864, partitioned from Boise County, and named for Ada Riggs, daughter of legislator H.C. Riggs, who established the county and co-founded Boise. Ada County ranks second in population among counties in the interior Pacific Northwest, behind only Spokane County, Washington.
Business & Permits
BUILDING & PERMITS
Office: Ada County Courthouse – 200 W. Front Street, Boise, ID | (208) 287-7500.
Notes: The Boise Valley was known to Native American tribes as “Peace Valley” for the peaceful gatherings historically held there at spiritual sites such as Eagle Rock, near the Old Idaho Penitentiary. Fort Boise was built near present-day Parma in 1834, and thousands of Oregon Trail pioneers rested along the Boise River between 1840 and 1860. Ada County’s first purpose-built courthouse was a three-story structure designed by Charles Ostner, built in 1882; a second courthouse, built 1938-1939 with Public Works Administration support in an Art Deco style with historical murals, is now on the National Register of Historic Places (1974) and has been repurposed as Idaho legislative offices; the current, third courthouse was completed 2000-2002 at a cost of $47 million.
Veterans Services
VETERANS SERVICES
Office: Ada County Veterans Services – confirm current contact via adacounty.id.gov.
Libraries
LIBRARIES
Ada Community Library / Boise Public Library – confirm current addresses/phones via the county library system.
Parks & Recreation
PARKS & RECREATION
Key Assets: The Old Idaho Penitentiary (historic site), the Boise River Greenbelt, and the WPA-era Old Ada County Courthouse (National Register of Historic Places) are the county’s premier heritage and recreational attractions.
Notes: The genuine, dramatic story of Ada County’s first sheriff turning organized crime figure is among the standout local historical facts covered in this project.
GIS & Maps
GIS & MAPS
Appraisal/Parcel Search: Ada County Assessor’s Office – confirm current contact via adacounty.id.gov.
Animal Services
ANIMAL SERVICES
Idaho Humane Society (serving Ada County animal control functions) – confirm current contact via idahohumanesociety.org.
Environmental & Waste
ENVIRONMENTAL / WASTE MANAGEMENT
Office: Ada County Environmental Health / Central District Health – confirm current contact via adacounty.id.gov.
NOTES: Ada County is the first county completed in Idaho’s Round 3 v2 redo, under the A+ sourced standard established for this project. The genuine, dramatic story of Ada County’s first sheriff, David C. Updyke, turning organized crime figure is among the standout local historical facts covered in this project. All contact information above was sourced via web search as of early August 2026 and should be reconfirmed directly with the relevant office before a visit, deadline-sensitive filing, or emergency-adjacent decision.
About Ada County
Ada County is Idaho’s most populous county and the core of the Treasure Valley – the broad, irrigated agricultural valley of the Snake and Boise Rivers that has become one of America’s fastest-growing regions. Boise, the county seat and state capital, is Idaho’s largest city and the anchor of a metropolitan statistical area growing at one of the fastest rates of any large metro in the nation. The Boise MSA grew at 2.2% in 2025 – 13th fastest nationally and 2nd fastest in the western US, trailing only St. George, Utah. The Treasure Valley’s cities of Meridian (Ada County’s second-largest city and one of Idaho’s fastest-growing), Eagle, Star, Kuna, and Garden City have absorbed much of the growth flowing from California, Washington, and Utah.
The growth drivers are well-established: lower housing costs than West Coast metros, no state income tax on retirement income, a rapidly diversifying economy, and high quality of life. Micron Technology – one of the world’s largest semiconductor manufacturers – is headquartered in Boise and the company’s announced expansion of its US manufacturing presence has generated significant economic anticipation. The College of Western Idaho and Boise State University provide higher education infrastructure. St. Luke’s Health System and Saint Alphonsus Regional Medical Center are major healthcare employers.
Ada County government is a three-member Board of Ada County Commissioners – which also serves as the Board of Equalization for property tax appeals – with elected offices for the Assessor, Clerk, Coroner, Prosecuting Attorney, Sheriff, and Treasurer.
All Services
Browse every category and topic available for this county.
The Ada County Assessor (190 E. Front Street, Suite 107, Boise, 208-287-7200) reassesses all real property annually as of January 1 of each tax year – reflecting current market conditions. Assessment notices are mailed in late May or early June. Idaho law limits annual property tax levy growth funded by property taxes to 3% – this is a levy cap on taxing districts, not a cap on individual property values, which can still rise with the market.
Homeowner’s Exemption: Idaho’s primary residential property tax relief. For owner-occupied primary residences, 50% of assessed value up to $125,000 is exempt from taxation. This exemption is substantial at current Boise-area values and must be applied for (once) through the Assessor’s office.
The BOE appeal process:
If you disagree with your assessed value, file an appeal with the Ada County Board of Equalization (200 W. Front Street, 3rd Floor, Boise, 208-287-7009). The deadline is the 4th Monday of June at 5:00 PM each year. File by email to [email protected], mail, deliver in person, or fax (208-287-7009). Do not wait until the last day – fax lines become congested.
The Board hears your appeal and issues a decision. Present comparable sales data, an independent appraisal, or a realtor’s written market analysis. The Board’s appeal concerns market value only – not the amount of your tax bill or your ability to pay.
After the BOE: If unsatisfied with the Board’s decision, file a notice of appeal with the Ada County Auditor within 30 days. The appeal goes to the Idaho Board of Tax Appeals (BTA) – a fully independent body in Boise (1673 W. Shoreline Drive, Suite 120, 208-334-3354). The BTA conducts a de novo hearing in Ada County and can raise, lower, or maintain the assessed value. Note: the BTA is not bound by the BOE’s decision, and the entire assessment – not just the challenged portion – is subject to BTA review.
Circuit Breaker (Property Tax Reduction Program): Qualifying low-income homeowners, including many seniors, may apply for a property tax reduction. Contact the Ada County Assessor for current income thresholds and application deadlines.
Tax payment: Annual bills paid in two installments – first half due December 20, second half due June 20. Late payments: 2% late charge plus 1% per month interest from January 1 of the following year.
Idaho has no state estate tax and no state inheritance tax – only federal estate tax applies.
OWNWELL CTA: Ada County BOE deadline: 4th Monday of June at 5 PM – don’t rely on fax on the last day. The BTA hears your case de novo and is not bound by the BOE’s decision; the entire assessment is in play. File the Homeowner’s Exemption if you haven’t – 50% up to $125,000 is significant. Ownwell manages the appeal with no upfront cost.
Recommended
Ada County BOE deadline: 4th Monday of June at 5 PM - don't rely on fax on the last day. The BTA hears your case de novo and is not bound by the BOE's decision; the entire assessment is in play. File the Homeowner's Exemption if you haven't - 50% up to $125,000 is significant. Ownwell manages the appeal with no upfront cost.
Courts & Legal
Courts & Legal
The Ada County District Court (200 W. Front Street, Boise, 208-287-6000) handles all civil, criminal, family, and probate matters for Ada County. The Ada County Clerk (208-287-6840) at the same address maintains all court records, land records – deeds, mortgages, and recorded documents – and vital records. Idaho property records are searchable online through the Ada County Assessor’s portal.
Idaho probate is governed by the Idaho Uniform Probate Code (Idaho Code Title 15). Idaho has no state estate tax and no state inheritance tax – only federal estate tax applies. Idaho recognizes Transfer on Death deeds for real property. Small estate affidavit procedures are available for qualifying estates.
Treasure Valley growth and real estate considerations: Ada County’s extraordinary growth has created some specific real estate and legal dynamics. New construction is prevalent throughout Meridian, Eagle, Star, and Kuna – and master-planned community CC&Rs, HOA structures, and builder warranty issues are routine legal matters. The influx of California transplants with California-issued trusts and estate plans often requires review for Idaho compatibility – California and Idaho have significant differences in community property rules and trust structures.
Senior Services: The Ada County Area Agency on Aging (208-376-7115) coordinates senior programming, home-delivered meals, transportation, SHIBA Medicare counseling (through the Idaho Department of Insurance), caregiver support, and connections to Idaho Medicaid long-term care programs. Idaho’s HCBS Waiver (Aged/Disabled) provides home and community-based care for qualifying seniors.
Genealogy
County-level record sources
Ada County Magistrate Court (probate/estate case files – see Probate section above).
Ada County is physically located in the same city (Boise) as the Idaho State Archives, giving direct local access to the statewide repository.
Local societies
No dedicated Ada-County-only genealogical society was confirmed in available directories beyond the statewide resources.
Probate & Estate
Losing someone and having to deal with courts and paperwork at the same time is hard. This section won’t make that easier, but it should tell you what to expect, what it costs, and where to go – so at least you’re not walking in blind.
Where to go
Ada County Magistrate Court (Fourth Judicial District) 200 West Front Street, Boise, ID 83702-7300 (208) 287-6900; Court Assistance Office: (208) 287-6963 Hours: Monday–Friday, 8:00 a.m.–5:00 p.m. Ada County is Idaho’s most populous county, home to Boise, the state capital.
Step 1: figure out which path applies
Idaho has adopted the Uniform Probate Code (Idaho Code Title 15), making its system one of the more streamlined in the country. Idaho is also a community property state – a combination shared with only a handful of other states. Idaho recognizes four main paths:
Small Estate Affidavit – a non-court process for estates with a total value of $100,000 or less (excluding liens and encumbrances) and no real property. Available 30 days after death. The affidavit (Affidavit for Collection of Personal Property) is obtained from the Court Assistance Office, signed before a notary, and presented directly to whoever holds the property – no court filing required (Idaho Code § 15-3-1201).
Summary Administration – available when the value of all the decedent’s property is less than the homestead allowance, exempt property, and last-illness medical expenses combined, or when there’s a surviving spouse who inherits everything as sole beneficiary. This is a streamlined court proceeding ending in a decree that vests the estate (Idaho Code §§ 15-3-1203, 15-3-1205).
Informal Probate – the most common track for uncontested estates, handled with minimal court involvement through the court registrar.
Formal Probate – court-supervised proceedings required when disputes arise, the will is contested, or other complexities demand judicial oversight.
Step 2: filing
For informal probate with a will, file an Application for Informal Probate of Will and Appointment of Personal Representative with the Magistrate Division in the county where the decedent was domiciled.
For formal probate, file a Petition for Probate of Will and Appointment of Personal Representative (or the equivalent petition for intestate estates).
Idaho does not have a statutory fee schedule for attorneys or personal representatives – fees must be reasonable based on the services rendered and the estate’s complexity.
If formal or informal probate is needed
Determine whether small estate affidavit, summary administration, or full probate applies, and identify community property versus separate property.
File the appropriate application or petition with the Ada County Magistrate Court.
Under informal proceedings, the registrar reviews the application without a hearing. Under formal proceedings, a judge holds a hearing.
The personal representative accepts the appointment and may need to post a bond, depending on the will’s terms or court order.
Once appointed, the court issues Letters Testamentary (testate) or Letters of Administration (intestate). Obtain several certified copies.
Publish notice to creditors as required; Idaho generally allows a claims period following notice.
Mail notice to all heirs, beneficiaries, and interested parties.
Marshal assets, obtain an EIN, open an estate account, pay valid debts and expenses, and prepare any required inventory.
Distribute remaining assets per the will or Idaho’s intestacy statutes (accounting for community property rules where applicable), then close the estate.
What it costs
Idaho does not impose its own state estate or inheritance tax.
Idaho does not have a statutory fee schedule for attorneys or personal representatives; fees must be reasonable based on services rendered and estate complexity.
Court filing fees and any publication costs are separate and should be confirmed directly with the Ada County Magistrate Court, since fees can change.
Probate in Idaho typically takes 6-12 months for uncontested estates.
Probate filings, estate administration, and guardianship matters are handled by the following office(s):
Health & Human Services
Public Health Information
PUBLIC HEALTH
Office: Central District Health (serving Ada County) – confirm current contact via cdh.idaho.gov.
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Recommended for Idaho
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