Texas is all over the place. It probably got hit by sign thieves in spots. At last check, Texas is a hold-out on joining the National Scenic Byways program
Oklahoma is pretty decent, but it tends to not sign the really, really old alignments. There may be good reasons for that, such as it going through residential areas, plus the pavement is a fragile in spots. It may be best for only hardcore roadies to know about those.
New Mexico is iffy. So is California.
Illinois is perhaps the best-signed of the states.
In terms of signage, Missouri has recently made a huge improvement with the installation of new "Historic Byways" signage.
Kansas and Arizona are also better than average.
