Tulsa County is a
county located in the
U.S. state of
Oklahoma. As of the
2010 census, the population was 603,403, making it the second-most populous county in Oklahoma, behind only
Oklahoma County. Its county seat and largest city is
Tulsa, the second-largest city in the state. Founded at statehood, in 1907, it was named after the previously established city of Tulsa. Before statehood, the area was part of both the
Creek Nation and the Cooweescoowee District of
Cherokee Nation in
Indian Territory.