1. The longest border between two states is between Texas and Oklahoma, so since Texas is green, Oklahoma must be orange.
    → OKLAHOMA-O
  2. Oklahoma’s clue tells us that Maine, Florida, and Washington are yellow.
    → MAINE-Y, FLORIDA-Y, WASHINGTON-Y
  3. Washington’s clue tells us that New Mexico cannot be yellow, and since it already borders a green and an orange state, Maine’s clue implies that New Mexico is purple.
    → NEW MEXICO-P
  4. The four most populous states are California, Texas, Florida, and New York. New Mexico’s clue says that three of those four states are the same color. Thus, California and New York are both green or yellow. Washington’s clue says that New York cannot be yellow, so California and New York are green.
    → CALIFORNIA-G, NEW YORK-G
  5. No states bordering the Pacific Ocean are purple, so Oregon must be orange, given its borders.
    → OREGON-O
  6. Oregon’s clue says that Kentucky is green.
    → KENTUCKY-G
  7. New York’s clue says that one state borders four purple states and another borders four orange states. The only two states that could do this while preserving Maine’s clue are Tennessee and Missouri. Missouri cannot border 4 purple states because of Oklahoma and Kentucky, so Missouri borders 4 orange states, which must mean Nebraska, Illinois and Tennessee are orange.
    → NEBRASKA-O, ILLINOIS-O, TENNESSEE-O
  8. Additionally, Tennessee must now border 4 purple states. Those states would have to be Missouri, Mississippi, Georgia, and Virginia.
    → MISSOURI-P, MISSISSIPPI-P, GEORGIA-P, VIRGINIA-P
  9. You can use Maine’s clue to determine the colors of Alabama, Arkansas, and Louisiana.
    → ALABAMA-G, ARKANSAS-Y, LOUISIANA-O
  10. Oregon’s clue says that Kentucky is the only green state on the Mississippi river, so Iowa, Wisconsin, and Minnesota cannot be green. Iowa must be yellow, then given its borders. That makes Wisconsin purple, and then Minnesota must be orange.
    → IOWA-Y, WISCONSIN-P, MINNESOTA-O
  11. Minnesota’s clue tells us that South Dakota and South Carolina have the same color. The only color that works is green. This makes North Dakota and North Carolina yellow.
    → SOUTH DAKOTA-G, SOUTH CAROLINA-G, NORTH DAKOTA-Y, NORTH CAROLINA-Y
  12. North Carolina’s clue says that Utah and Indiana are the same color. Utah does border the purple New Mexico, so the only color that works is yellow.
    → UTAH-Y, INDIANA-Y
  13. Utah being yellow means Arizona is orange, Nevada is purple, Colorado is green, Wyoming is purple. Therefore, Idaho is green, Montana is orange, and Kansas is yellow.
    → ARIZONA-O, NEVADA-P, COLORADO-G, WYOMING-P, IDAHO-G, MONTANA-O, KANSAS-Y
  14. Indiana’s clue implies that Rhode Island, the smallest state, is not green. Florida’s clue says that each color has the same number of contiguous states, meaning there are 12 of each color in the contiguous United States. There are only 9 green states revealed so far, so 3 more have to fit in the remaining states, without any of them bordering each other. This forces Michigan and New Hampshire to be green, as there is no way to arrange the remaining green states such that either Michigan or New Hampshire is not green.
    → MICHIGAN-G, NEW HAMPSHIRE-G
  15. The same logic in step 14 means that there must be 4 purple states remaining. This forces Ohio and Vermont to be purple.
    → OHIO-P, VERMONT-P
  16. Vermont’s clue says that either Delaware or Hawaii is purple. Hawaii cannot be purple due to California’s clue saying that Pacific-bordering states cannot be purple, so Delaware is purple. Since Washington’s clue says that New Jersey cannot be yellow, the only remaining color now for New Jersey is orange. Maine’s clue then makes Pennsylvania yellow, West Virginia orange, and Maryland green.
    → DELAWARE-P, NEW JERSEY-O, PENNSYLVANIA-Y, WEST VIRGINIA-O, MARYLAND-G
  17. Maryland’s clue says that yellow is the only color with 2 two-word states (North Dakota and North Carolina). Orange only has West Virginia and New Jersey so far, so Rhode Island must be orange to satisfy Maryland’s clue. This means that Connecticut is purple and Massachusetts is yellow. Also, Indiana’s clue says that Rhode Island and Alaska are the same color, so Alaska is orange
    → RHODE ISLAND-O, CONNECTICUT-P, MASSACHUSETTS-Y, ALASKA-O
  18. Massachusetts’ clue says that there is the same number of orange and green states. Orange currently has the 12 contiguous states plus Alaska, so Hawaii must be green.
    → HAWAII-G