I know for a fact both Texas and California have numbered county roads. The Central Expressway in Silicon Valley is Santa Clara County Route G6.

California's has some similarity to Wisconsins: state routes are numbered (e.g., S.R. 99 through the Central Valley), while county routes, instead of just letters like in Wisconsin, generally have a single-letter prefix (the prefixes vary by regions within the state) followed by a number.

(There are exceptions, though, as Lake and San Bernardino county routes are also just numbered, like state routes.)