Washington ? On the road to change, the quarters are halfway there.

The U.S. Mint’s 50-state quarter program, which began with Delaware and will end with Hawaii, reached the halfway mark last week with the debut of the Arkansas 25-cent piece.

Quarters are produced in the order that the states ratified the U.S. Constitution and joined the Union. The states come up with the designs, which feature images or themes honoring the state.

“Discovery and innovation has been the strongest theme,” as seen on the North Carolina, Virginia, Missouri and other state quarters, said Henrietta Holsman Fore, director of the Mint.

Most states also have opted for an outline of their state, she said. Other themes include the land and natural beauty, state capitals, liberty, courage and music.

Including the release of the Missouri coin, No. 24, the Mint has produced 20.8 billion state quarters since the program began in 1999.

How many quarters are minted depends on the country’s overall demand for coins, Fore said.

“If the economy is strong, it increases the usage of all coins and thus there is higher demand to mint and when the economy is slow there is less demand,” she said.

The three quarters with the highest mintage — Virginia, 1.59 billion, Connecticut, 1.35 billion, and South Carolina, 1.3 billion — all were made before the 2001 recession hit.

Philadelphia Mint Director Henrietta Holsman Fore shows a handful of freshly minted Arkansas quarters. The Arkansas coin is the 25th of 50 state quarters to be issued.

The Maine quarter has the lowest mintage, 448.8 million, followed by Missouri, 453.2 million, and Alabama, 457.4 million. All three coins were produced this year, as the economy struggled to gain firmer footing.

But in good economic times or bad, the state quarters have led to “a renaissance for coin collecting in America,” Fore said.

Roughly 130 million Americans collect the state quarters, Fore said. “That represents at least one state quarter collector in every household,” she added.

“Americans collect the quarters because they will be scarce. We mint a quarter for 10 weeks and 10 weeks only and we will never mint it again,” she said.

The Arkansas quarter, unveiled Oct. 28, is the 25th state quarter and features the image of a diamond, rice stalks and a mallard flying above a lake. It was the last of the state quarters released in 2003.

For 2004, the five state quarters to be released are Michigan, Florida, Texas, Iowa and Wisconsin.