I went through the list and think I'm up to 15.
Here are the one's I've done.
#6. San Juan Mountain Skyway. Only a portion, Cortez-Durango.
#8. Twisty Road Next 140 miles!! California Hwy 36. Red Bluff to the coast.
#9. Arkansas Pig Tail, Hwy 23. I may have done only parts of this one.
#12. The Grand Staircase-Escalante National Monument. Hwy 12 in Utah.
#20. Coronado Trail. Hwy 191 (the old hwy 666) in Arizona.
#27. Central Hills Loop. Black Hills, South Dakota.
#28. Rattlesnake Pass to Wallowa Lake, Oregon to Washington, Hwy 3+126.
#32. The Incredible North Shore Tour....***Only by car*** so I won't count it.
#33. Mexican Hat to Bryce Canyon. Utah, only part of the route.
#45. The Lolo Pass. Hwy 12 across Idaho. Many times!!
#54. Big Horn Mountain loop. A route over the Big Horn Mts. on Hwy's 14 and 16. Most of it!
#55. Heber to Hannah & the Wolf Creek Pass Loop. Outside of Park City, UT. Most of it!
#58. Arkansas At Its Best - Highway 7. Parts north of I-40.
#66. The Devil's Tail. Devils Canyon area of Oregon.
#85. Hwy 16 from the Pig Trail to Scenic 7. Through Deer, Arkansas.
#90. Yuba River Ride. Part of it along CA-49
How many have you done??