When was Washington County founded?

Washington County was founded in 1788, and named after George Washington.

What is the county seat of Washington County?

The county seat of Washington County is Marietta.

Is there an online parcel map for Washington County?

Yes. Ohio Geographically Referenced Information Program (OGRIP, Ohio DAS) statewide compilation of county auditor parcels publishes a parcel map of 62,009 parcels, rated fallback here. You can click any parcel on it in Parcel Chart's free map, no sign-in needed.

Has Washington County's boundary or name changed?

Washington County was created in 1788. Since then the Atlas of Historical County Boundaries records 23 later changes, chiefly involving Morgan County, Athens County and Jefferson County.

Who issues building permits in Washington County?

The county's page on building permits: Permits. Inside a city or town, ask that city first.

Who issues septic and well permits in Washington County?

The county's page on septic systems and wells: Behavioral Health Board.

Is my lot in a flood zone?

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

County · code 39167

Washington CountyOhio

Washington County is in Ohio, with its county seat in Marietta. The county was created on July 27, 1788 by the Northwest Territory and is named after George Washington.

Founded1788
County seatMarietta
Named forGeorge Washington
Land area632 sq mi + 8 sq mi water
Population59,771 2020 Census
Parcels mapped62,009 checked 14 October 2026

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

Updated 20 October 2026

Census outline · seat marked

History

Founded in 1788

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

Washington County was created by the Northwest Territory on July 27, 1788 from non-county area and part of the Western Reserve, with an implicit challenge to Connecticut's authority in the region going unanswered. The county lost territory repeatedly in its early years: to Hamilton in 1792, to Adams, Jefferson, and Ross in 1797–1798, and to Fairfield, Belmont, Gallia, and Columbiana between 1800 and 1804. Washington County became a county in the state of Ohio on March 1, 1803.

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

1788
Washington County created Washington created by the Northwest Territory from non-county area and part of the Western Reserve. This implicit challenge to Connecticut's authority in the Western Reserve went unanswered. 27 July 1788 · Terr. Papers U.S., 3:278-279; Chase, 3:ch. 330/p. 2096; Cappon, Petchenik, and Long, 92
1792
Lost territory Washington lost to Hamilton.
to Hamilton
11 February 1792 · Terr. Papers U.S., 3:363-364
1797
Lost territory Washington lost to creation of Adams.
to Adams
10 July 1797 · Terr. Papers U.S., 2:612-613; Chase, 3:ch. 333/p. 2096
1797
Lost territory Washington lost to creation of Jefferson.
to Jefferson
29 July 1797 · Terr. Papers U.S., 2:617-618; Chase, 3:ch. 334/p. 2096
1803
Became part of Ohio Washington became a county in the state of Ohio. 1 March 1803 · U.S. Stat., vol. 2, ch. 40 [1802], secs. 1-3/pp. 173-174; Van Zandt, 112

Show all 24 changes (19 more)

1788
Washington County created Washington created by the Northwest Territory from non-county area and part of the Western Reserve. This implicit challenge to Connecticut's authority in the Western Reserve went unanswered. 27 July 1788 · Terr. Papers U.S., 3:278-279; Chase, 3:ch. 330/p. 2096; Cappon, Petchenik, and Long, 92
1792
Lost territory Washington lost to Hamilton.
to Hamilton
11 February 1792 · Terr. Papers U.S., 3:363-364
1797
Lost territory Washington lost to creation of Adams.
to Adams
10 July 1797 · Terr. Papers U.S., 2:612-613; Chase, 3:ch. 333/p. 2096
1797
Lost territory Washington lost to creation of Jefferson.
to Jefferson
29 July 1797 · Terr. Papers U.S., 2:617-618; Chase, 3:ch. 334/p. 2096
1798
Lost territory Washington lost to creation of Ross.
to Ross
20 August 1798 · Terr. Papers U.S., 3:510; Chase, 3:ch. 336/p. 2097
1799
Lost territory Washington lost to Jefferson.
to Jefferson
19 December 1799 · Chase, 3:ch. 342/p. 2098
1800
Lost territory Washington lost to creation of Fairfield.
to Fairfield
9 December 1800 · Terr. Papers U.S., 3:526; Chase, 3:ch. 340/pp. 2097-2098
1801
Lost territory Washington lost to creation of Belmont.
to Belmont
7 September 1801 · Terr. Papers U.S., 3:528; Chase, 3:ch. 341/p. 2098
1803
Became part of Ohio Washington became a county in the state of Ohio. 1 March 1803 · U.S. Stat., vol. 2, ch. 40 [1802], secs. 1-3/pp. 173-174; Van Zandt, 112
1803
Lost territory Washington lost to creation of Gallia.
to Gallia
30 April 1803 · Ohio Laws 1803, 1st assy., ch. 8/p. 19; Chase, 3:ch. 347/pp. 2100-2101
1803
Lost territory Washington lost to creation of Columbiana.
to Columbiana
1 May 1803 · Ohio Laws 1803, 1st assy., ch. 6/p. 15; Chase, 3:ch. 346/p. 2100
1804
Lost territory Washington lost to creation of Muskingum and implicitly lost small area to Columbiana.
to Muskingum to Columbiana
1 March 1804 · Ohio Laws 1803, 2d assy., ch. 6, secs. 1-4/pp. 68-70; Chase, 3:ch. 349/p. 2101
1805
Lost territory Washington lost to creation of Athens.
to Athens
1 March 1805 · Ohio Laws 1804, 3d assy., ch. 68/p. 283; Chase, 3:ch. 351/p. 2102
1807
Lost territory Washington lost to Jefferson.
to Jefferson
31 January 1807 · Ohio Laws 1806, 5th assy., ch. 37/p. 104; Ohio Laws 1826, 25th assy., gen., p. 15; Chase, 3:ch. 358/p. 2104 and ch. 454/p. 2141
1808
Exchanged territory Washington exchanged with Athens.
with Athens
18 February 1808 · Ohio Laws 1807, 6th assy., ch. 43/p. 149; Chase, 3:ch. 366/pp. 2107-2108
1813
Lost territory Washington lost to creation of Monroe; Monroe not fully organized, part attached to Washington for administrative and judicial purposes.
to Monroe
29 January 1813 · Ohio Laws 1812, 11th assy., ch. 25/p. 57; Chase, 3:ch. 396/p. 2117
1814
Exchanged territory Washington exchanged with Athens.
with Athens
10 February 1814 · Ohio Laws 1813, 12th assy., ch. 49/p. 146; Chase, 3:ch. 398/p. 2118
1815
Lost territory Washington lost to Monroe; Monroe fully organized, detached from Washington.
to Monroe
1 March 1815 · Ohio Laws 1814, 13th assy., ch. 36, secs. 1, 2, 6/pp. 128-129; Chase, 3:ch. 402/pp. 2120-2121
1817
Lost territory Washington lost to creation of Morgan; Washington was separated into two parts by this creation. Morgan not fully organized, part attached to Washington for administrative and judicial purposes.
to Morgan
29 December 1817 · Ohio Laws 1817, 16th assy., ch. 18/p. 42; Chase, 3:ch. 414/p. 2126
1818
Lost territory Washington lost to creation of Perry.
to Perry
1 March 1818 · Ohio Laws 1817, 16th assy., ch. 11, secs. 1, 5/pp. 26, 29; Chase, 3:ch. 411/p. 2124
1819
Changed Morgan fully organized, detached from Washington.
Morgan
1 March 1819 · Ohio Laws 1818, 17th assy., ch. 6, secs. 1, 4/pp. 7-9; Chase, 3:ch. 421/pp. 2129-2130
1845
Lost territory Washington lost to Morgan.
to Morgan
11 March 1845 · Ohio Laws 1844, 43d assy., loc., p. 360
1846
Lost territory Washington lost to Morgan.
to Morgan
14 February 1846 · Ohio Laws 1845, 44th assy., loc., p. 105
1851
Lost territory Washington lost to creation of Noble and lost to Monroe and Morgan, including section 11, township 8, range 12, which had been left with Washington on 11 March 1845.
to Noble to Monroe to Morgan
1 April 1851 · Ohio Laws 1850, 49th assy., loc., secs. 1-2, 4, 10/pp. 137-139

Land and parcels

What the maps cover in Washington

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

Parcels Fallback

Lot lines and tax-map numbers for 62,009 parcels from Ohio Geographically Referenced Information Program (OGRIP, Ohio DAS) statewide compilation of county auditor parcels. Drawn for tax purposes: usually within a few feet of a survey, but not a survey. This copy is a fallback, not the county's own: use it as a guide and check the official record.
edited 23 September 2026 · checked 14 October 2026
Address points Official

One point per address, 32,921 in all from Ohio Geographically Referenced Information Program (OGRIP), Ohio DAS/OIT (state GIS office).
edited 24 June 2025 · checked 13 October 2026
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

Washington by the Census

Population

59,771 2020 Census count

Housing units

27,987 2020 Census count

Land area

632 square miles

Water area

8 square miles

People per sq mi

95 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.

Records

Assessor and property recordsfrom washingtongov.org · checked 14 October 2026
Clerk of court: deeds and plats
Clerk of the Courts
from washingtongov.org · checked 14 October 2026

Permits

Health department: septic and wellfrom washingtongov.org · checked 14 October 2026
Permitsfrom washingtongov.org
Plumbing Permitsfrom washingtongov.org
Water Well Logsfrom washingtongov.org
Septic System Inspectionsfrom washingtongov.org

Zoning and code

Planning and zoningfrom washingtongov.org · checked 14 October 2026
Zoningfrom washingtongov.org
Building or Zoning Permitfrom washingtongov.org

County government

County government
The official website of Washington County.
washingtongov.org

See your own lot on these maps

Open Washington 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 Washington County

When was Washington County founded?: Washington County was founded in 1788, and named after George Washington.
What is the county seat of Washington County?: The county seat of Washington County is Marietta.
Is there an online parcel map for Washington County?: Yes. Ohio Geographically Referenced Information Program (OGRIP, Ohio DAS) statewide compilation of county auditor parcels publishes a parcel map of 62,009 parcels, rated fallback here. You can click any parcel on it in Parcel Chart's free map, no sign-in needed.
Has Washington County's boundary or name changed?: Washington County was created in 1788. Since then the Atlas of Historical County Boundaries records 23 later changes, chiefly involving Morgan County, Athens County and Jefferson County.
Who issues building permits in Washington County?: The county's page on building permits: Permits. Inside a city or town, ask that city first.
Who issues septic and well permits in Washington County?: The county's page on septic systems and wells: Behavioral Health Board.
Is my lot in a flood zone?: We do not have flood maps for Washington County yet. Look up the address on FEMA's Flood Map Service Center, which shows the effective flood map for any lot.

Nearby