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County · code 39109

Miami CountyOhio

Miami County is a county in Ohio with its seat in Troy, formed in 1807 from Montgomery County.

  • Founded1807
  • County seatTroy
  • Named forMiami people
  • Land area407 sq mi + 3.1 sq mi water
  • Population108,774 2020 Census
  • Parcels mapped54,280 checked 16 October 2026
Open the free map Click any parcel in Miami County: acreage, parcel id, address and who publishes the map. No sign-in.

Updated

ShelbyMontgomeryDarke Troy Census outline · seat marked

Where it is

Miami on the map of Ohio

Ohio has 88 counties and county equivalents, each with its own records office. Shapes with a page are links.

Adams CountyAllen CountyAshland CountyAshtabula CountyAthens CountyAuglaize CountyBelmont CountyBrown CountyButler CountyCarroll CountyChampaign CountyClark CountyClermont CountyClinton CountyColumbiana CountyCoshocton CountyCrawford CountyCuyahoga CountyDarke CountyDefiance CountyDelaware CountyErie CountyFairfield CountyFayette CountyFranklin CountyFulton CountyGallia CountyGeauga CountyGreene CountyGuernsey CountyHamilton CountyHancock CountyHardin CountyHarrison CountyHenry CountyHighland CountyHocking CountyHolmes CountyHuron CountyJackson CountyJefferson CountyKnox CountyLake CountyLawrence CountyLicking CountyLogan CountyLorain CountyLucas CountyMadison CountyMahoning CountyMarion CountyMedina CountyMeigs CountyMercer CountyMonroe CountyMontgomery CountyMorgan CountyMorrow CountyMuskingum CountyNoble CountyOttawa CountyPaulding CountyPerry CountyPickaway CountyPike CountyPortage CountyPreble CountyPutnam CountyRichland CountyRoss CountySandusky CountyScioto CountySeneca CountyShelby CountyStark CountySummit CountyTrumbull CountyTuscarawas CountyUnion CountyVan Wert CountyVinton CountyWarren CountyWashington CountyWayne CountyWilliams CountyWood CountyWyandot CountyMiami County Miami
Counties of Ohio · Miami highlighted

History

Formed in 1807 from Montgomery County

An old deed may name a county that no longer exists, or a boundary that has since moved.

Miami was created from Montgomery in 1807 and named after the Miami people. Between 1809 and 1819, Miami lost territory to the creation of Darke County and Shelby County.

Boundary changes from the Newberry Library, Atlas of Historical County Boundaries.

  1. 1807
    Miami County created Miami created from Montgomery.
    from Montgomery
    · Ohio Laws 1806, 5th assy., ch. 32, secs. 1-2, 5/pp. 94-96; Chase, 3:ch. 357/p. 2104
  2. 1809
    Lost territory Miami lost to creation of Darke; Darke not fully organized, attached to Miami for administrative and judicial purposes.
    to Darke
    · Ohio Laws 1808, 7th assy., ch. 6/p. 69; Chase, 3:ch. 373/p. 2110
  3. 1812
    Changed Part of Montgomery lying north of the Indian Boundary reverted to Non-County Area 6 attached to Darke and Non-County Area 7 attached to Miami. Non-County Area 6 attached to Darke was attached indirectly through Darke to Miami. Attachments were for administrative and judicial purposes.
    MontgomeryDarke
    · Ohio Laws 1811, 10th assy., ch. 13/p. 22; Chase, 3:ch. 390/p. 2115
  4. 1817
    Changed Darke fully organized, detached fron Miami.
    Darke
    · Ohio Laws 1816, 15th assy., ch. 4/p. 5; Chase, 3:ch. 406/p. 2122
  5. 1819
    Lost territory Miami lost to creation of Shelby; Non-County Area 7 detached from Miami, attached to Shelby for administrative and judicial purposes.
    to Shelby
    · Ohio Laws 1818, 17th assy., ch. 12, secs. 1, 7/pp. 21-23; Chase, 3:ch. 422/pp. 2130-2131

Land and parcels

What the maps cover in Miami

Who publishes each layer, how good it is, and when we last checked.

Official
from the office that keeps the record
Good enough
a reliable statewide or national copy
Fallback
a guide only; check the official record
Missing
nothing public found yet

People and land

Miami by the Census

Population
108,774 2020 Census count
Housing units
46,766 2020 Census count
Land area
407 square miles
Water area
3.1 square miles
People per sq mi
268 population ÷ land area

Source: US Census Bureau, 2020 Census; US Census Bureau, 2020 Gazetteer Files. Not endorsed or certified by the Census Bureau.

Rules and offices

Who to ask before you build, dig or sell

Official county pages only. We link to them; we do not copy them, because they change.

Inside a city or town, permits usually come from that city rather than the county.

Permits

Zoning and code

County government

See your own lot on these maps

Open Miami County on Parcel Chart's free map and click your parcel. Save it with a free account; the full record of your place (site map, projects, documents) is Pro, in early access.

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Questions

Common questions about Miami County

When was Miami County founded?
Miami County was founded in 1807, formed from Montgomery County, and named after Miami people.
What is the county seat of Miami County?
The county seat of Miami County is Troy.
Is there an online parcel map for Miami County?
Yes. A public source publishes a parcel map of 54,280 parcels, rated good enough here. You can click any parcel on it in Parcel Chart's free map, no sign-in needed.
Has Miami County's boundary or name changed?
Miami County was created in 1807 from Montgomery County. Since then the Atlas of Historical County Boundaries records 4 later changes, chiefly involving Darke County, Montgomery County and Shelby County.
Who issues building permits in Miami County?
The county's page on building permits: Permits. Inside a city or town, ask that city first.
Is my lot in a flood zone?
We do not have flood maps for Miami County yet. Look up the address on FEMA's Flood Map Service Center, which shows the effective flood map for any lot.

Nearby

Counties next door