Dexter Marsh was born in Montague in 1806. He moved with his family to Greenfield, Massachusetts in 1834 and began working as a laborer, handyman, and courthouse janitor. In 1835, Marsh noticed that the patterns in the red sandstone slabs he was laying down resembled large bird tracks too large to be created by any living bird. Marsh recognized that the tracks, more than being simple curiosities, had been created by living animals, and found similar tracks in other stones in the area.

Marsh was the first to collect and study the many fossil tracks that are found in the Connecticut River Valley. Traveling in a flat boat he had built himself, Marsh went up and down the Connecticut collecting fossils. He eventual amassed one of the most extensive collections of dinosaur tracks in the United States and earned national recognition as a paleontologist.

In 1846 Marsh was elected a member of the American Association for the advancement of Science. In 1952 he became a member of the Lyceum of Natural History in New York, and the Academy of Natural Science in Philadelphia.

When Marsh died in 1853, he left behind a collection that included 400 to 500 slabs of stone containing 1000 tracks. This collection was auctioned off for a large sum, and a portion was purchased by Edward Hitchcock, a professor at Amherst College. Hitchcock added the tracks to the growing Amherst College Iconological collection, and later they were housed in the Pratt Museum.

The collection covers Dexter Marsh's financial activity from 1830 to 1853, including expense books, journals, day books, bills, receipts, and a deed. The collection also includes two registers of visitors to his home in Greenfield, which housed his fossil collection until his death. The second register also contains some journal entries made by Marsh's wife from 1853-1858. One photograph of Marsh is also included.