Motown, n. — Green’s Dictionary of Slang

Motown n.

[the home of Motown record company, itself named after the city’s original nickname Motor City n.]

(US) Detroit, Michigan.

1977		(con. 1969) M. Herr Dispatches 178: There were a lot of white guys [...] coming on to Day Tripper about his hometown, calling it Dodge City or Motown.
1978		T. O’Brien Going After Cacciato (1980) 138: Coonsville, MoTown, Sin City.