Crater of Diamonds State Park is a 911-acre Arkansas state park in Pike County, Arkansas, in the United States. The park features a 37.5-acre plowed field, one of the few diamond-bearing sites accessible to the public. Diamonds have been discovered in the field continuously since 1906, including the graded-perfect Strawn-Wagner Diamond, found in 1990, and the Uncle Sam, found in 1924, which at over 40 carats is the largest diamond ever found in the United States.