The Great Raft was a gigantic log jam or series of "rafts" that clogged the Red and Atchafalaya Rivers and was unique in North America in terms of its scale.
The Great Raft probably began forming around 1100–1200. It grew faster at its upper end than it decayed or washed out at the lower end, leading to its peak length spanning more than 160 miles/250 km in the early 1830s. The raft, at one point, extended for 165 miles from Loggy Bayou to Carolina Bluffs. The Great Raft formed part of the mythology of the local Caddo tribe and protected them from competing tribes, as well as intermittently flooding land and making it fertile for agriculture.
At the beginning of the 19th century, the Raft extended from Campti, Louisiana, to around Shreveport, Louisiana. The raft blocked the mouth of Twelvemile Bayou, impeding settlement in the area west of Shreveport. There were many smaller logjams on the Red River.
The raft raised the banks of the river, forming bayous and making several lakes, called the Great Raft Lakes and including Caddo and Cross Lakes, along the lower reaches of Red River tributaries.
Steamboat builder and river captain Henry Miller Shreve (1785–1851) began systematically removing the Great Raft, a task that was continued by others until the latter part of the 19th century. For his efforts, the city of Shreveport was named after him.
When Shreve began work the Raft was 8 miles directly below to 17 miles directly above Shreveport.
Captain Shreve had removed the raft up to the mouth of Twelvemile Bayou in April 1835. Shreve concluded this work in 1838, having removed the last impediment to navigation on the Red River.
Although Shreve had completely removed the raft, it reformed later farther up the river. The new foot was at the head of the old Raft. This was near today's Belcher, Louisiana. The second Raft gradually extended until it reached the Arkansas state line. Lieutenant Eugene Woodruff succeeded in removing this second raft in 1873.