Unknown maker. Colors employed by probable artist, Thomas Moran, are spectacular. The Green River Formation is an Eocene geologic formation that records the sedimentation in a group of intermountain lakes in three basins along the present-day Green River in Colorado, Wyoming, and Utah. Wikipedia. The scene also captures a large band of Native Americans riding along the lake in the foreground. Puzzle is cut tightly and must be disassembled carefully, preferably in dry weather.