Rankin is a borough in Allegheny County, Pennsylvania, United States, 8 miles south of Pittsburgh on the Monongahela River. The borough was named after Thomas Rankin, a local landowner. Early in the 20th century, Rankin specialized in manufacturing steel and wire goods. The population increased from 3,775 in 1900 to 7,470 in 1940 and has since declined to 1,896 as of the 2020 census.