(NEXSTAR) — For a decade, the U.S. Mint produced some of the most commonly collected coins – the 50 State Quarters.

Just as the name implies, a separate quarter was minted for every state during the program, which ran from 1999 to 2008, according to the U.S. Mint. Every year, five new quarters were issued, following the order in which the states ratified the Constitution or were admitted into the Union.

On the reverse of each is a unique design of state features or iconic moments in history. The Kansas quarter, for example, features a buffalo and sunflowers – the state animal and state flower, respectively. New York’s quarter features the state, the Statue of Liberty, and the slogan “Gateway to Freedom,” a nod to Ellis Island.

The South Dakota state quarter, issued in 2006, features Mount Rushmore, our state bird the pheasant, and two heads of wheat.

The South Dakota state quarter, first released in 2006. (Getty)

The Mint produced 510.8 million South Dakota state quarters, which were minted in Denver and Philadelphia. It’s one of the more difficult state quarters to find.

If you do have a South Dakota state quarter, it could be worth more than 25 cents — though not by much.

Those that are in mint condition and marked with a D or P (meaning they were produced in Denver or Philadelphia) could be worth as much as $1.10, according to Coin Trackers. The site also reports that a South Dakota quarter marked with an S (meaning it was minted in San Francisco) could be worth $6, however, the Mint does not report that any were produced there.

A silver-proof South Dakota state quarter could be worth as much as $15.

How can you tell if your South Dakota quarter, or any money you’ve been collecting, is worth more than its intended value?

“The answer is not always obvious,” Dustin Johnson, Vice President of Numismatics (the study or collection of coins, paper money, and medals) at Heritage Auctions previously explained to Nexstar. “Odd items are always set aside but that doesn’t make them rare or terribly valuable.”

It’s best to take your money to a verified coin expert, like Heritage Auctions, which can evaluate your item for free.