Many NPSL teams have rivalries given the close geography of the teams throughout the league. The most notable rivalry was the Rust Belt Derby contested between Detroit City FC, AFC Cleveland, and FC Buffalo. The name refers to the teams' shared region, the Rust Belt. Another intense rivalry existed between the San Diego Flash and San Diego Boca/Force FC, which were crosstown rivals in San Diego. Until the 2013 sale and rebranding of Force FC from Boca FC, the ownership groups of the two clubs were previously partners in the original San Diego Flash club of the A-League that competed from 1998 to 2001.
