What was the purpose of lewis and clark expedition? How long did it last?

May 1804 through September 1806. It was made to find a practical route through the west of the US. they were sent to map and explore the entire territory.

Hey There

The answer to your question should be The Lewis and Clark expedition last exactly Two years, four months and Lewis and Clark expedition was meant to explore the territories that had been acquired by the United States through the Louisiana Purchase in 1803.