This painting is likely imagined, the setting inspired by lakes that Heald frequented, like Clark and Hubert, but unfortunately, there were not any Elk in central Minnesota at the time that Heald would have painted this, so it was not done from life.
Thief Lake Wildlife Management Area. “Minnesota Elk Past and Present.” Minnesota Department of Natural Resources, n.d. http://files.dnr.state.mn.us/recreation/hunting/elk/management.pdf.