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County · code 26017

Bay CountyMichigan

Bay County is in Michigan, with Bay City as its county seat, and covers 442.4 square miles. The county was created on April 20, 1857, from parts of Midland, Saginaw, and Arenac counties, and was named after Saginaw Bay.

  • Founded1857
  • County seatBay City
  • Named forSaginaw Bay
  • Land area442 sq mi + 188 sq mi water
  • Population103,856 2020 Census
  • Parcels mapped52,297 checked 14 October 2026
Open the free map Click any parcel in Bay County: acreage, parcel id, address and who publishes the map. No sign-in.

Updated

ArenacSaginawMidlandGladwinTuscola Bay City Census outline · seat marked

Where it is

Bay on the map of Michigan

Michigan has 83 counties and county equivalents, each with its own records office. Shapes with a page are links.

Alcona CountyAlger CountyAllegan CountyAlpena CountyAntrim CountyArenac CountyBaraga CountyBarry CountyBenzie CountyBerrien CountyBranch CountyCalhoun CountyCass CountyCharlevoix CountyCheboygan CountyChippewa CountyClare CountyClinton CountyCrawford CountyDelta CountyDickinson CountyEaton CountyEmmet CountyGenesee CountyGladwin CountyGogebic CountyGrand Traverse CountyGratiot CountyHillsdale CountyHoughton CountyHuron CountyIngham CountyIonia CountyIosco CountyIron CountyIsabella CountyJackson CountyKalamazoo CountyKalkaska CountyKent CountyKeweenaw CountyLake CountyLapeer CountyLeelanau CountyLenawee CountyLivingston CountyLuce CountyMackinac CountyMacomb CountyManistee CountyMarquette CountyMason CountyMecosta CountyMenominee CountyMidland CountyMissaukee CountyMonroe CountyMontcalm CountyMontmorency CountyMuskegon CountyNewaygo CountyOakland CountyOceana CountyOgemaw CountyOntonagon CountyOsceola CountyOscoda CountyOtsego CountyOttawa CountyPresque Isle CountyRoscommon CountySaginaw CountySt. Clair CountySt. Joseph CountySanilac CountySchoolcraft CountyShiawassee CountyTuscola CountyVan Buren CountyWashtenaw CountyWayne CountyWexford CountyBay County Bay
Counties of Michigan · Bay highlighted

History

Formed in 1857 from Midland County, Saginaw County, Arenac County and Iosco County

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

Bay County was created from Midland, Saginaw, and Arenac counties in 1857; Arenac was eliminated in the process, though Iosco was authorized to be attached to Bay. The county gained territory from Saginaw in 1871 and 1881, and gained the Charity Islands from Huron in 1880. In 1883, Bay County lost territory when Arenac County was re-created.

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

  1. 1857
    Bay County created Bay created from Midland, Saginaw, and all of Arenac; Arenac eliminated. Iosco was authorized to be attached to Bay, but Iosco had been fully organized on 16 February 1857.
    from Midlandfrom Saginawfrom Arenacfrom Iosco
    · Mich. Acts 1857, reg. sess., no. 171, secs. 1-2, 15/pp. 438-439, 441; Mich. Rpts., 5:114
  2. 1859
    Boundary clarified Bay boundaries redefined (no change); mistake of 20 April 1857, attaching Iosco to Bay, was corrected (no change).
    with Ioscono change
    · Mich. Acts 1859, reg. sess., no. 97/p. 255
  3. 1871
    Gained territory Bay gained from Saginaw.
    from Saginaw
    · Mich. Acts 1871, reg. sess., no. 448/p. 194
  4. 1880
    Gained territory Bay gained the Charity Islands from Huron.
    from Huron
    · Mich. Acts 1879, reg. sess., pub., no. 265/p. 287
  5. 1881
    Gained territory Bay gained from Saginaw.
    from Saginaw
    · Mich. Acts 1881, reg. sess., loc., no. 414/p. 343
  6. 1883
    Lost territory Bay lost to re-creation of Arenac.
    to Arenac
    · Mich. Acts 1883, reg. sess., pub., no. 35/p. 25

Land and parcels

What the maps cover in Bay

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

Bay by the Census

Population
103,856 2020 Census count
Housing units
48,562 2020 Census count
Land area
442 square miles
Water area
188 square miles
People per sq mi
235 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

Bay County's official site

We have found the county's site but not its offices yet; start there.

County government

See your own lot on these maps

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Questions

Common questions about Bay County

When was Bay County founded?
Bay County was founded in 1857, formed from Midland County, Saginaw County, Arenac County and Iosco County, and named after Saginaw Bay.
What is the county seat of Bay County?
The county seat of Bay County is Bay City.
Is there an online parcel map for Bay County?
Yes. A public source publishes a parcel map of 52,297 parcels, rated good enough here. You can click any parcel on it in Parcel Chart's free map, no sign-in needed.
Has Bay County's boundary or name changed?
Bay County was created in 1857 from Midland County, Saginaw County, Arenac County and Iosco County. Since then the Atlas of Historical County Boundaries records 4 later changes, chiefly involving Saginaw County, Arenac County and Huron County.
Is my lot in a flood zone?
We do not have flood maps for Bay 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