On the recent Condo Week trip to Pennsylvania, I went through the last 4 counties of Indiana. That makes 35 states where I've now been to all the counties. Here's what's left:
Alaska (which has no counties)
California, 3 counties left
Georgia, oodles & gobs of counties left
Montana, 7 counties left
Idaho, 2 counties left
Iowa, 10 counties left
Kentucky, 8 counties left, which I should pass through in a few months
Massachusetts, 2 counties left (both islands)
Michigan, 20 counties left, all in the lower peninsula
Missouri, 1 county left
Nebraska, 10 counties left
North Carolina, 1 county left, which I should pass through in a few months
Oregon, 12 counties left
Tennessee, 3 counties left, which I should pass through in a few months
and Washington, 2 counties left