My oldest son (8 1/2 years old) has always had a fascination with U.S. geography and the history of the states. This game combines both.
To make your own deck of states cards, download the 7-page PDF I made here. Print on cardstock.
If you're worried the cards will be see-through, spritz the back of the printed pages with spray glue (in a well-ventilated area) and adhere a lightweight piece of scrapbook paper to the glued side before cutting out.
Now grab your kid and get ready to play.
Shuffle the deck and divide it in half with the cards face down. Each player turns over the top card on their deck, keeping it to themselves. Then, the youngest player names a category (e.g. population, number of counties, electoral votes, etc.).
The opponent reads the number from that category on their card and the youngest player does the same. For all categories but one, the player with the largest number is the winner and takes the opponent's card, setting both their card and their opponent's card in a pile in front of them face up.
If a player selects the "statehood" category, the winner is the player with the card containing the earliest statehood year.
The player that wins the round selects the category for the next one.
If the category called results in both players announcing the same number from their cards (e.g. both states have the same number of electoral votes), two more cards are drawn and compared. The player to win, takes all four cards.
When the decks are out of cards, players compare the number of collected cards from their wins. You can count them or straighten and set the decks side-by-side. The player with the most cards wins.