The trivia question about state capitals not on the interstate system got a different answer in 2012, and now the connection is complete.
The final segment of I-580 running south from Reno to Carson City NV opened Aug. 2. (Interstate pictures: AA Roads) It covered a southeast bypass of Carson City and also carries US 395 and US 50. A northeast bypass was signed as I-580 in 2012 when another part of the new interstate opened to the north.
I-580 is only the second signed child route of I-80 between the San Francisco Bay Area and Lincoln; I-180 in Cheyenne is the other.
Now, of the four states whose capitals aren’t connected to the interstate system, two border Iowa: Missouri and South Dakota. That might be a stretch to get the Iowa angle, but the interstate significance and the final shift of US 50 off the Lincoln Highway through Carson City are both notable.