In the spring of 1810, Manuel Lisa sent Andrew and Pierre Menard with a party of about 30 men and John Colter as a guide to the Three Forks area to build a trading post. The resulting fort, Fort Three Forks, was one of the ﬁrst trading posts between the Missouri and the Paciﬁc Coast. The fort was built as a base for trapping beaver over the entire area of the Missouri River and its branches above the Great Falls.
Life was always interesting at the Fort. Eight of the party were killed by raiding Blackfeet Indians. When they weren't harassed by Indians, critters like rattlesnakes and grizzlies kept them on their toes. The business of beaver trapping was so hazardous that the fort was abandoned in 1811.
Nothing is left of the fort today. Time and the meandering river have destroyed most of the ground the fort stood on. A modern motel with the forts name stands nearby the original site. However, an anonymous surveyor has given us a description of the fort: A double stockade of logs set three feet deep, enclosing an area of 300 sq. feet situated upon the tongue of land about a half a mile wide, between the Jefferson and Madison Rivers, about two miles above the conﬂuence, upon the south bank of the channel of the former stream, now called the Jefferson Slough. The store and warehouse were built on each side of the gates, and on the other side next to the interior of the fort, two buildings were connected by a gate, the space between buildings and stockade ﬁlled in with pickets, making a large strong room without any covering overhead. In each store, about ﬁve feet from the ground, was a whole 18 inches square, with a strong shutter fastening inside, opening into the enclosed space between the gates.
When the Indians wanted to trade, the inner gate was closed; a man would stand at the outer gate until a number of Indians had passed in and then lock the outer gate. He would then climb through the trading hole into the store. The Indians would pass whatever each one had to trade through the hole into the store and the trader would throw out of the hole whatever the Indians wanted to the value of the article received.