William Ressler was born on a farm in Lancaster County, Pennsylvania.  He entered the Philadelphia College of Art in 1947, where he studied illustration under Henry Pitz and Albert Gold, and watercolor under J. Frank Copeland and W. Emerton Heitland.  He graduated in 1951, receiving the Thornton Oakley Medal for achievement in illustration.

Ressler has created extraordinarily detailed watercolor paintings, featuring a wide range of themes, from Biblical scenes to the Philadelphia cityscape. 

Ressler is a member of the Philadelphia Watercolor Club and the American Watercolor Society.  His drawings and paintings are included in several private, corporate, and university collections.

His awards have included an honorable mention from the Allied Artists of America in 1972 and the Second Prize in Watercolor, Stone Harbor, 1972, 1973, and 1976 Annual Exhibitions.  He was also the winner of the 25th Anniversary Wetlands Institute Limited Edition Print competition in 1997.