This is Caldwell Jefferson or Jefferson Caldwell.

1850, 8th Ward, Chicago, Cook Co., p379 lines 31 through 33, Oct. 7, 1850

John Dempsey 35, grocer, (IRE?), Joseph 5; Jefferson Caldwell 27, black, Cook, born Kentucky.

He is the only "of color" within pages of the census in this predominantly then-Irish neighborhood. Hope someone can use this.