Gregor founded the school of painters called the Heartland painters. The group acquired its name because of the emphasis it places on the Midwestern landscape. Rockford Art Museum in Rockford, Illinois, held a retrospective of Gregor?s work in 1993-1994. His work appears in numerous notable private and public collections throughout the United States and Europe. He also has exhibited internationally for many years. The 1993-1994 National Endowment for the Arts Grant award and the Illinois Academy of Fine Arts Lifetime Achievement Award are among the numerous grants and awards he has received during his long career in art. Gregor taught at Illinois State University from 1970-1995 and was instrumental in the formation of its exceptional art program. He was awarded the Distinguished Professor of Art, Emeritus and Adjunct in June 1995. He has also participated in several workshops and artist in residence programs throughout the United States.