As boring as it is, the best I can figure is that I could do 11 states (if you include DC) by basically just doing the quickest possible way to DC from here. I-70 east to Pennsylvania (with the northern bypass of St. Louis), US40 down to I-68, back to I-70, I-270, I-495, GW Parkway.
CO-KS-MO-IL-IN-OH-WV-PA-MD-VA-DC
Or I could do a southern route and go CO-KS-OK-MO-AR-TN-MS-AL-GA-SC-(GA)-NC by:
I-70, I-135, KS196, Local Roads, US400, Visit KS/MO/OK tripoint, US400, I-44, MO360, US60, US63, I-555, I-55, I-269, I-22, I-65, I-20, I-85, SC11, SC28, GA28 to the GA/NC border.
It's tough out here in the big states.
Chris