How much is an 1999 Connecticut quarter with and upside down head worth?

A 1999 Connecticut quarter with an upside-down head is likely a minting error known as a "misaligned die" or "die rotation." While typical Connecticut quarters are worth their face value of 25 cents, coins with such errors can be worth more to collectors, typically ranging from a few dollars to potentially over $50, depending on demand and condition. For an accurate valuation, it's best to consult a coin collector or a reputable dealer.