|— City —|
|Motto: "America"s Friendliest City"|
|Counties||Allen, Van Wert|
|• Mayor||Michael Gallmeier|
|• Total||3.48 sq mi (9.01 km2)|
|• Land||3.44 sq mi (8.91 km2)|
|• Water||0.04 sq mi (0.10 km2)|
|Elevation||774 ft (236 m)|
|• Estimate (2011)||7,075|
|• Density||2,064.2/sq mi (797.0/km2)|
|Time zone||Eastern (EST) (UTC-5)|
|• Summer (DST)||EDT (UTC-4)|
|GNIS feature ID||1056973|
Delphos is located at (40.844441, -84.339360).
2010 census 
As of the census of 2010, there were 7,101 people, 2,893 households, and 1,865 families residing in the city. The population density was 2,064.2 inhabitants per square mile (797.0 /km2). There were 3,137 housing units at an average density of 911.9 per square mile (352.1 /km2). The racial makeup of the city was 97.5% White, 0.4% African American, 0.2% Native American, 0.2% Asian, 0.4% from other races, and 1.3% from two or more races. Hispanic or Latino of any race were 1.8% of the population.
There were 2,893 households out of which 31.2% had children under the age of 18 living with them, 48.3% were married couples living together, 11.0% had a female householder with no husband present, 5.2% had a male householder with no wife present, and 35.5% were non-families. 29.9% of all households were made up of individuals and 13.8% had someone living alone who was 65 years of age or older. The average household size was 2.41 and the average family size was 3.00.
The median age in the city was 38.6 years. 24.6% of residents were under the age of 18; 8.8% were between the ages of 18 and 24; 23.8% were from 25 to 44; 25.5% were from 45 to 64; and 17.1% were 65 years of age or older. The gender makeup of the city was 48.6% male and 51.4% female.
2000 census 
As of the census of 2000, there were 6,944 people, 2,717 households, and 1,880 families residing in the city. The population density was 2,391.9 people per square mile (924.5/km²). There were 2,906 housing units at an average density of 1,001.0 per square mile (386.9/km²). The racial makeup of the city was 98.63% White, 0.27% African American, 0.14% Native American, 0.19% Asian, 0.24% from other races, and 0.52% from two or more races. Hispanic or Latino of any race were 0.76% of the population.
There were 2,717 households out of which 33.8% had children under the age of 18 living with them, 55.2% were married couples living together, 9.9% had a female householder with no husband present, and 30.8% were non-families. 27.2% of all households were made up of individuals and 13.8% had someone living alone who was 65 years of age or older. The average household size was 2.52 and the average family size was 3.08.
In the city the population was spread out with 26.8% under the age of 18, 9.6% from 18 to 24, 27.6% from 25 to 44, 19.6% from 45 to 64, and 16.4% who were 65 years of age or older. The median age was 36 years. For every 100 females there were 95.9 males. For every 100 females age 18 and over, there were 88.6 males.
The median income for a household in the city was $35,817, and the median income for a family was $44,385. Males had a median income of $32,917 versus $21,124 for females. The per capita income for the city was $16,380. About 5.6% of families and 6.8% of the population were below the poverty line, including 7.5% of those under age 18 and 6.6% of those age 65 or over.
Delphos City Schools include Jefferson High School. Jefferson High School sports participate in the Northwest Conference, an athletic body sanctioned by the Ohio High School Athletic Association (OHSAA); their mascot is the Wildcat. St. Johns is the citys private school.
The city was founded amidst the Great Black Swamp in 1844 on the Miami and Erie Canal by the German-born Reverend John Otto Bredeick and his brother Ferdinand Bredeick, both from Verl, Germany. The Canal brought early prosperity to the community, providing access to Toledo and Cincinnati. By the 20th century, the Canal had declined in importance, but railroads provided access to markets.
Three Delphos buildings are listed on the National Register of Historic Places: the Marks-Family House and St. John's Catholic Church on the Allen County side of the city, and the Bredeick-Lang House on the Van Wert County side.
Notable people 
- Zane Grey - a famous author
- Leslie Peltier - amateur astronomer and prolific discoverer of comets and variable stars.
- "US Gazetteer files 2010". United States Census Bureau. Retrieved 2013-01-06.
- "US Board on Geographic Names". United States Geological Survey. 2007-10-25. Retrieved 2008-01-31.
- "American FactFinder". United States Census Bureau. Retrieved 2013-01-06.
- "Population Estimates". United States Census Bureau. Retrieved 2013-01-06.
- "American FactFinder". United States Census Bureau. Retrieved 2008-01-31.
- "US Gazetteer files: 2010, 2000, and 1990". United States Census Bureau. 2011-02-12. Retrieved 2011-04-23.
- "National Register Information System". National Register of Historic Places. National Park Service. 2009-03-13.
|Wikimedia Commons has media related to: Delphos, Ohio|
- City website
- Chamber of Commerce
- Delphos Public Library
- Delphos Herald
- WDOH 107.1
- Ohio Lincoln Highway Historic Byway