“Frank Spier, our beloved chief,” reads the caption of this photograph taken during the 1886 expedition to the Badlands. Spier, Class of 1877, was identified by a newspaper article about the trip as “a gentleman of scientific training and wide experience in the western country.”

Princeton Party at Twin Lakes. The photo was taken during the first expedition, in 1877. Top row, second from left, is Henry Fairfield Osborn ’77, who became a famous paleontologist and museum curator.

A stereoscopic view listed as “Heads of Mountain Sheep,” taken in the Dakotas during the 1877 trip.

Mount Elbert, the highest summit of the Rocky Mountains, in the background, 1877.

The 1877 Princeton party, pictured in Cheyenne, Wyo.

The handwritten caption for this image reads: “Bad Lands, Miocene Cretaceous.” It was taken during the 1890 expedition.

Images from an 1890 photo album. The expedition to the Dakotas began at Fort Robinson, Neb.; the students were accompanied by an Indian guide, the fort’s junior physician, and several cavalrymen.

More shots from the photo album, 1890. Students included in the captions include Arthur Gladwin 1891, Cornelius Agnew 1891, and Edwin Lewis 1891.