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Seneca County, Ohio facts for kids

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Seneca County
Seneca County Justice Center in Tiffin, Ohio
Seneca County Justice Center in Tiffin, Ohio
Official seal of Seneca County
Map of Ohio highlighting Seneca County
Location within the U.S. state of Ohio
Map of the United States highlighting Ohio
Ohio's location within the U.S.
Country  United States
State  Ohio
Founded April 1, 1824
Named for the Seneca nation
Seat Tiffin
Largest city Tiffin
 • Total 553 sq mi (1,430 km2)
 • Land 551 sq mi (1,430 km2)
 • Water 1.8 sq mi (5 km2)  0.3%
 • Total 55,069
 • Density 99.58/sq mi (38.45/km2)
Time zone UTC−5 (Eastern)
 • Summer (DST) UTC−4 (EDT)
Congressional district 4th

Seneca County is a county located in the northwestern part of the U.S. state of Ohio. As of the 2020 census, the population was 55,069. Its county seat is Tiffin. The county was created in 1820 and organized in 1824. It is named for the Seneca Indians, the westernmost nation of the Iroquois Confederacy, which was based in present-day New York but had territory into Pennsylvania and Ohio.

Seneca County comprises the Tiffin, OH Micropolitan Statistical Area, which is also included in the Findlay-Tiffin, OH Combined Statistical Area.


The county was barely inhabited until the 1830s, but by 1860 its population had massively increased to about half the current number of inhabitants. It grew slowly thereafter, with periods of more marked increase towards the end of the 19th century, during the Great Depression and the post–World War II baby boom. In 1980 it was censused at 61,901, and has been declining since. Since about 2000, the county's population declines by about 100–300 persons annually, mainly due to a migration deficit of about 300 persons annually. This decline is projected to continue in the future.


According to the U.S. Census Bureau, the county has a total area of 553 square miles (1,430 km2), of which 551 square miles (1,430 km2) is land and 1.8 square miles (4.7 km2) (0.3%) is water.

Almost 80% of the county's total area is agricultural land. Some 10% is covered by forest, and the rest is mostly taken up by built-up areas and to a slightly lesser extent by pastureland.

The terrain of Seneca County is nearly level, gently sloping from about 290 meters ASL in the southeast to about 210 m ASL at the edge of the erstwhile Great Black Swamp in the northwest. Most of the county's area is located between 230 and 260 m ASL however. Almost the entire county belongs to the Sandusky River drainage basin; the river itself bisects the county from north to south slightly west of its middle, running through Tiffin as it does so. There is some steeper terrain along the rivers's course, formed by the occasional ravine of its tributaries.

Despite the presence of the Great Lakes which make for a somewhat milder climate in the region, Seneca County has a rather continental climate, namely after removal of the forests which once covered most of it upset the microclimate. Winters can be harsh, with plentiful snowfall due to lake-effect snow, and summers are often hot and sometimes oppressively humid, bordering on subtropical. The mostly featureless surface can result in rather extreme wind chill. In a 1906 description, the local climate was actually described as "rather unhealthful".

Adjacent counties


Historical population
Census Pop.
1830 5,159
1840 18,128 251.4%
1850 27,104 49.5%
1860 30,868 13.9%
1870 30,827 −0.1%
1880 36,947 19.9%
1890 40,869 10.6%
1900 41,163 0.7%
1910 42,421 3.1%
1920 43,176 1.8%
1930 47,941 11.0%
1940 48,499 1.2%
1950 52,978 9.2%
1960 59,326 12.0%
1970 60,696 2.3%
1980 61,901 2.0%
1990 59,733 −3.5%
2000 58,683 −1.8%
2010 56,745 −3.3%
2020 55,069 −3.0%
U.S. Decennial Census
1790-1960 1900-1990
1990-2000 2020

2010 census

As of the 2010 United States Census, there were 56,745 people, 21,774 households, and 14,870 families residing in the county. The population density was 103.0 inhabitants per square mile (39.8/km2). There were 24,122 housing units at an average density of 43.8 per square mile (16.9/km2). The racial makeup of the county was 93.7% white, 2.3% black or African American, 0.6% Asian, 0.2% American Indian, 1.3% from other races, and 1.9% from two or more races. Those of Hispanic or Latino origin made up 4.4% of the population. In terms of ancestry, 47.6% were German, 10.4% were Irish, 8.9% were American, and 8.2% were English.

Of the 21,774 households, 31.4% had children under the age of 18 living with them, 51.6% were married couples living together, 11.3% had a female householder with no husband present, 31.7% were non-families, and 26.3% of all households were made up of individuals. The average household size was 2.49 and the average family size was 2.97. The median age was 38.8 years.

The median income for a household in the county was $42,573 and the median income for a family was $51,216. Males had a median income of $39,494 versus $30,286 for females. The per capita income for the county was $20,976. About 8.7% of families and 11.9% of the population were below the poverty line, including 17.9% of those under age 18 and 8.3% of those age 65 or over.


Major highways

  • US 23.svg U.S. Route 23
  • US 224.svg U.S. Route 224

Other highways

  • OH-4.svg State Route 4
  • OH-12.svg State Route 12
  • OH-18.svg State Route 18
  • OH-19.svg State Route 19
  • OH-53.svg State Route 53
  • OH-67.svg State Route 67
  • OH-100.svg State Route 100
  • OH-101.svg State Route 101
  • OH-162.svg State Route 162
  • OH-228.svg State Route 228
  • OH-231.svg State Route 231
  • OH-587.svg State Route 587
  • OH-590.svg State Route 590
  • OH-635.svg State Route 635
  • OH-778.svg State Route 778


  • Bandit Field Airdrome
  • Fostoria Metropolitan Airport
  • Seneca County Airport
  • Weiker Airport


Map of Seneca County Ohio With Municipal and Township Labels
Map of Seneca County, Ohio With Municipal and Township Labels




  • Adams
  • Big Spring
  • Bloom
  • Clinton
  • Eden
  • Hopewell
  • Jackson
  • Liberty
  • Loudon
  • Pleasant
  • Reed
  • Scipio
  • Seneca
  • Thompson
  • Venice

Census-designated places

Unincorporated communities

Places of interest

Natural history

Before widespread settlement, the area of Seneca County was for the most part woodland. Besides the fringe of the Great Black Swamp in the northwest, there was also an extensive area of marshland in the Bloomville area as well as smaller patches of swamp terrain which were formed due to the county's essentially level terrain. Native American inhabitants and later settlers used the region mainly for hunting fur animals, with little agriculture of note until the early 19th century.

Starting in the early-mid 19th century, the county's area was subject to wholesale deforestation. This led to massive alteration of much of the local wildlife, with grassland and farmland animals replacing the native woodland fauna. Migrant waterbirds, in ancient times commonly encountered throughout the region as they foraged in the swamps on their way south, are nowadays rare and concentrate on the few remaining waterbodies large enough to sustain them. The passenger pigeon (Ectopistes migratorius) had several roosting (and probably nesting) places in the county when it was still wooded. Removal of the forest had driven the birds away by the 1860s, foreshadowing its eventual total extinction due to large-scale logging which rendered this species unable to sustain the massive hunting pressure.

Several species of waterbirds, formerly frequently encountered during migration, are only rarely seen nowadays. These include, for example, the common loon (Gavia immer), American wigeon (Anas americana), redhead (Aythya americana), canvasback (Aythya valisneria), and several species of mergansers.

Landbirds were apparently less seriously affected; apart from the passenger pigeon, the ruffed grouse (Bonasa umbellus), wild turkey (Meleagris gallopavo), golden eagle (Aquila chrysaetos) and marsh wren (Cistothorus palustris) had essentially or completely disappeared by 1900. However, it is not known how many of the numerous species of New World warblers, most of which today only occur only as transient migrants, formerly bred in Seneca County.

The Eskimo curlew (Numenius borealis), possibly extinct today, occurred as a transient in Ohio until about 1900; to what extent it migrated through Seneca County is not well known but even if it did it is unlikely that it was often seen after deforestation had gotten underway in earnest. The extinct Carolina parakeet (Conuropsis carolinensis) – or probably individuals of the western subspecies, the Louisiana Parakeet (C. c. ludovicianus) – may have on occasion have occurred in Seneca County as a vagrant before 1862.

The only record of the long-billed murrelet (Brachyramphus perdix) in Ohio comes from Seneca County. A stray individual of this North Pacific auk was observed and photographed between November 12–18, 1996. The rare Kirtland's warbler (Setophaga kirtlandii) is again increasing in numbers and may occasionally range as far north as Seneca County.

The introduced house sparrow (Passer domesticus) is common since at least the late 19th century. The ring-necked pheasant (Phasianus colchicus), another species introduced from Europe, never seems to have become really plentiful, though it has been a breeding resident since at least 1901.

See also

Kids robot.svg In Spanish: Condado de Seneca (Ohio) para niños

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