When was Summit County founded?

Summit County was founded in 1854, formed from Green River County, Great Salt Lake County and Salt Lake County.

What is the county seat of Summit County?

The county seat of Summit County is Coalville.

Is there an online parcel map for Summit County?

Yes. Summit County publishes a parcel map of 43,980 parcels, rated good enough here. You can click any parcel on it in Parcel Chart's free map, no sign-in needed.

Has Summit County's boundary or name changed?

Summit County was created in 1854 from Green River County, Great Salt Lake County and Salt Lake County. Since then the Atlas of Historical County Boundaries records 11 later changes, chiefly involving Rich County, Uintah County and Cache County.

Is my lot in a flood zone?

We do not have flood maps for Summit County yet. Look up the address on FEMA's Flood Map Service Center, which shows the effective flood map for any lot.

County · code 49043

Summit CountyUtah

Summit County is a county in Utah that was created on January 13, 1854, by Utah Territory. The county seat is Coalville.

Founded1854
County seatCoalville
Land area1,871 sq mi + 10 sq mi water
Population42,357 2020 Census
Parcels mapped43,980 checked 14 October 2026

Open the free map Click any parcel in Summit County: acreage, parcel id, address and who publishes the map. No sign-in.

Updated 20 October 2026

Census outline · seat marked

History

Formed in 1854 from Green River County, Great Salt Lake County and Salt Lake County

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

Summit County was created from Green River, Great Salt Lake, and Salt Lake counties. In 1861, Summit County was fully organized and detached from Great Salt Lake County. The county gained territory from Green River County in 1872 when Green River was eliminated. Summit County lost territory to Wyoming Territory in 1868 and to the creation of Uintah County in 1880.

Boundary changes from the Newberry Library, Atlas of Historical County Boundaries; the 5 that matter most are shown first.

1854
Summit County created Summit created by Utah Territory from Green River (Utah Territory, extinct) and Great Salt Lake (now Salt Lake); Summit included territory in present Utah and Wyoming. Summit not fully organized, attached to Great Salt Lake "for election, revenue, and judicial purposes."
from Green Riverfrom Great Salt Lakefrom Salt Lake
13 January 1854 · Utah Terr. Laws 1853, 3d sess., pp. 14-15
1856
Lost territory Summit lost to creation of Cache.
to Cache
5 January 1856 · Utah Terr. Laws 1855, 5th sess., sec. 5/p. 6
1862
Gained territory Summit gained from Davis and Great Salt Lake (now Salt Lake); exchanged with Green River (Utah Territory, extinct); lost to creation of Morgan and Wasatch, and lost to Cache and Weber.
from Davis from Great Salt Lake from Salt Lake from Green River from Morgan from Wasatchfrom Cachefrom Weber
17 January 1862 · Utah Terr. Laws 1861, 11th sess., sec. 14/pp. 49-50
1868
Summit County created The United States created Wyoming Territory from Dakota, Idaho, and Utah Territories. Summit lost to Wyoming Territory and was eliminated from present Wyoming. 25 July 1868 · U.S. Stat., vol. 15, ch. 235[1868], secs. 1, 17/pp. 178, 183; Van Zandt, 136, 144
1896
Became part of Utah Summit became a county in the state of Utah. 4 January 1896 · U.S. Stat., vol. 28, ch. 138 [1894]/pp. 107-112; U.S. Stat., vol. 29, procl. no. 9, [1896]/pp. 876-877; Van Zandt, 159

Show all 13 changes (8 more)

1854
Summit County created Summit created by Utah Territory from Green River (Utah Territory, extinct) and Great Salt Lake (now Salt Lake); Summit included territory in present Utah and Wyoming. Summit not fully organized, attached to Great Salt Lake "for election, revenue, and judicial purposes."
from Green Riverfrom Great Salt Lakefrom Salt Lake
13 January 1854 · Utah Terr. Laws 1853, 3d sess., pp. 14-15
1856
Lost territory Summit lost to creation of Cache.
to Cache
5 January 1856 · Utah Terr. Laws 1855, 5th sess., sec. 5/p. 6
1861
Changed Summit fully organized; detached from Great Salt Lake (now Salt Lake).
Great Salt LakeSalt Lake
4 March 1861 · Summit County Record Book A, p. 1
1862
Gained territory Summit gained from Davis and Great Salt Lake (now Salt Lake); exchanged with Green River (Utah Territory, extinct); lost to creation of Morgan and Wasatch, and lost to Cache and Weber.
from Davis from Great Salt Lake from Salt Lake from Green River from Morgan from Wasatchfrom Cachefrom Weber
17 January 1862 · Utah Terr. Laws 1861, 11th sess., sec. 14/pp. 49-50
1866
Boundary clarified Summit boundaries were clarified (no change).
no change
10 January 1866 · Utah Terr. Laws 1865, 15th sess., ch. 146, sec. 18/p. 209
1868
Summit County created The United States created Wyoming Territory from Dakota, Idaho, and Utah Territories. Summit lost to Wyoming Territory and was eliminated from present Wyoming. 25 July 1868 · U.S. Stat., vol. 15, ch. 235[1868], secs. 1, 17/pp. 178, 183; Van Zandt, 136, 144
1872
Gained territory Summit gained all of Green River (Utah Territory); Green River eliminated. Summit lost small area to Rich near town of Wasatch.
from Green Riverfrom Rich
16 February 1872 · Utah Terr. Laws 1872, 20th sess., ch. 19, sec. 1/p. 28 and ch. 25, p. 40
1880
Lost territory Summit lost to creation of Uintah.
to Uintah
18 February 1880 · Utah Terr. Laws 1880, 24th sess., ch. 10/pp. 11-12
1896
Became part of Utah Summit became a county in the state of Utah. 4 January 1896 · U.S. Stat., vol. 28, ch. 138 [1894]/pp. 107-112; U.S. Stat., vol. 29, procl. no. 9, [1896]/pp. 876-877; Van Zandt, 159
1917
Gained territory Summit gained from Uintah.
from Uintah
5 March 1917 · Utah Laws 1917, 12th sess., chs. 34, 113/pp. 102-104, 336-337
1917
Lost territory Summit lost to Rich (later overturned). Eastern boundary with Uintah was confirmed.
to Rich to Uintah
8 May 1917 · Utah Laws 1917, 12th sess., ch. 113, pp. 336-337
1918
Lost territory Summit lost to creation of Daggett.
to Daggett
7 January 1918 · HRS Utah, Daggett, 11-12; Dunham and Dunham, 319
1921
Gained territory Summit gained from Rich when Utah Supreme Court ruled the act of 8 May 1917 unconstitutional.
from Rich
19 January 1921 · "Summit County v. Rich County," in Utah Rpts., 57:553-564

Land and parcels

What the maps cover in Summit

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

Parcels Good enough

Lot lines and tax-map numbers for 43,980 parcels from Summit County. Drawn for tax purposes: usually within a few feet of a survey, but not a survey.
checked 14 October 2026
Address points Missing

No public address points layer found for Summit County yet.
Buildings Reference

Roof outlines traced from aerial imagery from FEMA Response Geospatial Office with Oak Ridge National Laboratory (ORNL). Good for seeing what is on a lot; not accurate enough to set a fence from.
checked 18 October 2026

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

Summit by the Census

Population

42,357 2020 Census count

Housing units

25,674 2020 Census count

Land area

1,871 square miles

Water area

10 square miles

People per sq mi

23 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

Summit County's official site

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

County government

County government
The official website of Summit County.
co.summit.ut.us

See your own lot on these maps

Open Summit 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.

Open the free map no sign-in Pro early access

Questions

Common questions about Summit County

When was Summit County founded?: Summit County was founded in 1854, formed from Green River County, Great Salt Lake County and Salt Lake County.
What is the county seat of Summit County?: The county seat of Summit County is Coalville.
Is there an online parcel map for Summit County?: Yes. Summit County publishes a parcel map of 43,980 parcels, rated good enough here. You can click any parcel on it in Parcel Chart's free map, no sign-in needed.
Has Summit County's boundary or name changed?: Summit County was created in 1854 from Green River County, Great Salt Lake County and Salt Lake County. Since then the Atlas of Historical County Boundaries records 11 later changes, chiefly involving Rich County, Uintah County and Cache County.
Is my lot in a flood zone?: We do not have flood maps for Summit County yet. Look up the address on FEMA's Flood Map Service Center, which shows the effective flood map for any lot.

Nearby