Green’s Dictionary of Slang

(US tramp/Und.) Sacramento, California.

1891		Morn. Appeal (Carson City, NV) 30 Sept. 3/3: Horses that win in Sac — Sacramento where the heat is sweltering — [are] six seconds slower.
1905		S.F. Call 30 Nov. 16/5: ‘I’m going back to Sac, where I came from.’ ‘Going back where?’ inquired the Judge. ‘Sac — Sacramento, you know’.
1931		Irwin Amer. Tramp and Und. Sl. 162: Sac.–Sacramento, Calif.
1962		Ragen & Finston World’s Toughest Prison 816: Sac – Sacramento, California.