One of his most notable works is the equestrian statue of Confederate States of America General James Longstreet erected in 1998 at Gettysburg National Military Park.

[3][4] Casteel is a proponent of establishing a National Civil War Memorial.

When he was in the fourth grade in school, he decided that he wanted to become a sculptor after seeing a photo of Michelangelo's David.

[1] He gained experience through apprenticeships with American and European sculptors, including the Pucci family[6] of marble carvers from Pietrasanta, Italy.

[7][3] He operates his own studio and art gallery in Gettysburg, Pennsylvania.