Knoxville, Tennessee is 2.2 times larger than Pittsburgh.
Area: 332 km2 calculated
Knoxville is a city in the U.S. state of Tennessee, and the county seat of Knox County. The city had a population of 178,874 as of the 2010 census and an estimated population of 183,270 in 2013, making it the state's third largest city. Wikipedia
Area: 153 km2 calculated
Pittsburgh is the seat of Allegheny County and with a population of 305,841 is the second-largest city in the U.S. state of Pennsylvania. With a metropolitan CSA population of 2,659,937, it is the largest in both the Ohio Valley and Appalachia and the 20th-largest in the U.S. Wikipedia