The population was 36,837 at the 2010 census. According to the US Census 2008 estimate Ohio's Columbus–Marion–Chillicothe Combined Statistical Area has 2,002,604 people. Marion is the county's largest city and the center of the Marion Micropolitan Statistical Area (as defined by the United States Census Bureau in 2003). President Warren G. Harding was a resident of Marion for much of his adult life.
The city and its development were closely related to industrialist Edward Huber and his extensive business interests. The city is home to several historic properties, some listed on the National Register of Historic Places listings in Marion County, Ohio.
The origins of Marion can be traced back to the War of 1812 when Jacob Foos, a surveyor for General Harrison's army, discovered a spring at the top of a hill and established a well there which was named "Jacob's Well". At the time it was a stopover for troops on their way from Ft. Franklin (Columbus) to Toledo. Legend has it that in the middle of the night Foos awoke with a terrible thirst. He began to dig and told his fellow travelers that he was going to dig till he found either water or hell. This well was located near what is now Marion Towers on Delaware Ave. The town of Marion was platted north of Jacob's Well in 1822 by Alexander Holmes with Eber Baker as his agent (Proprietor - administrator) for selling off the village lots. Marion County was officially recognized in 1824. Like the county in which it is located, the city was named in honor for General Francis Marion.
Marion was one of Ohio's major industrial centers until the 1970s. Products of the Marion Steam Shovel Company (later Marion Power Shovel) built the Panama Canal and in the 1960s, NASA contracted with Power Shovel to construct the crawler-transporters that moved the assembled Saturn V rockets, used by Project Apollo, to the launch pad. In 1911, 80% of the nation's steam shovel and heavy duty earth moving equipment was manufactured in Marion, Ohio.
The city is also a rail center for CSX, and Norfolk Southern. Marion is the nation's leader in corn and popcorn produced foods. Whirlpool Corporation of Benton Harbor, Michigan is the largest employer in the city operating the largest clothes dryer manufacturing facility in the world.