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. In this 1999 realistic landscape titled Illinois Landscape #156 Gregor handles color in an abstract manner. This method of handling color separates him from the regional landscape painters who were popular at the turn of the twentieth century. Gregor also paints in another style which utilizes an aerial perspective where the landscapes are viewed from above. He calls this series of paintings ?Flatscapes.