Ontario is a city in Richland County in the U.S. state of Ohio. It is part of the Mansfield, Ohio Metropolitan Statistical Area. The population was 5,303 at the 2000 census. Ontario is a major regional retail hub serving the entire North-Central Ohio area, with a shopping population of over 150,000.
The original town of Ontario started as a settlement in Springfield Township near Mansfield. In 1834, the Ontario settlement combined with another small settlement known as New Castle.
Ontario is located on a major east-west transportation corridor that was originally known in the early 1900s as "Ohio Market Route 3." This route was chosen in 1913 to become part of the historic Lincoln Highway which was the first road across America, connecting New York City to San Francisco. The arrival of the Lincoln Highway to Ontario was a major influence on the development of the town. Upon the advent of the federal numbered highway system in 1928, the Lincoln Highway through Ontario became U.S. Route 30.