Been to 38: (Virtually of these I had spent at the very least a day or night there, and / or drove across. None of this "had a connecting flight in an airport" stuff)
1. Alabama
Arizona
California
Colorado
5. Connecticut
Delaware
Florida
Georgia
Idaho
10. Illinois
Indiana
Iowa
Kentucky
Maine
15. Maryland
Massachusetts
Michigan
Minnesota
Montana
20. Nebraska
Nevada
New Hampshire
New Jersey
New York
25. North Carolina
North Dakota
Ohio
Pennsylvania
Rhode Island
30. South Carolina
South Dakota
Tennessee
Utah
Vermont
35. Virginia
West Virginia
Wisconsin
Wyoming
Can't recall being in 12:
1. Alaska
Arkansas
Hawaii
Kansas
5. Louisiana
Mississippi
Missouri
New Mexico
Oklahoma
10. Oregon
Texas
Washington
Basically I'm missing a big chunk in the bottom middle of the country. (I think it's pretty clear what route my next cross-country trip is gonna take,) the pacific northwest, Alaska and Hawaii.