Sotheby's expects the deed to sell for $80,000 to $120,000, many times the value of the St. Louis land transaction it records, The St. Louis Post-Dispatch reports. It is to be auctioned Thursday.

Lewis and Clark are best known for their expedition to the Pacific Northwest between 1804 and 1806. In 1809, when Lewis sold several parcels of land to Pierre Chouteau, the founder of St. Louis, he was governor of the Louisiana Territory.

A few weeks later, Lewis died of a gunshot, probably self-inflicted, on the Natchez Trace in Tennessee.

Aside from the official reports of their expedition, only a few documents bear the signatures of both Lewis and Clark. Both men were living in St. Louis in 1809, with Clark serving as Indian agent for the Louisiana Territory.

The document is from the collection of Dr. Robert Small of New York.