Complex sentence: In 1999, the 50 State Quarters program of circulating commemorative quarters began; these have a modified Washington obverse and a different reverse for each state, ending the former Washington quarter's production completely.
Split into simpler sentences: In 1999, the 50 State Quarters program of circulating commemorative quarters began. These have a modified Washington obverse and a different reverse for each state, ending the former Washington quarter's production completely.