Note 1) The following Eppens' biographic materials are provided by Askart.com:

"William H. Eppens was born December 25, 1885 in Lincoln, Nebraska. He came to Chicago in 1907, where he studied at the School of the Art Institute of Chicago and the Academy of Fine Arts.

“He prefers to paint landscape in oil and his hunting ground is in Cook County. He says the windows of the house on the hill have the golden windows, when we are in the valley; but when we go to the hill top the golden windows were right in the house in the valley. So why run away to paint lovely things when they are so near us?”

Studio: 6210 Ingleside Avenue, Chicago, Illinois. The artist died October 8, 1956 in Chicago.

Sources:
Catalog: Century of Progress exhibition by artists of Illinois. 1933. Additional information from the Illinois Historical Art Project.

Note 2) The auction records of Askart.com, make clear that Eppens' watercolors sell for between $300-$400; and thus, warrant a conclusion that the above presale estimate of $300-$400 is reasonable and justifiable.