You could knit one color across as one strip in which case, cast on 37 + 38 + whatever, and knit top down, 1 color stripe. Or for each stripe, put all the states that cast on 37 in one red/white up/down strip and change colors. (and then all the ones that cast on 38 in another strip)
Or add one stockinette stitch to all the 37-across instructions, either just after the first K3 or just before the last K3 and modify the patterns (or delete one stitch in all the 38 across ones...)
I think those suggestions would work - anyone else?
If you are industrious, you could knit them in the order of statehood! It's a great project.