The sioux indian attacks on stagecoach lines.
<span>The causes of the Sand Creek massacre
were rooted in the long conflict for control of the Great Plains of
eastern Colorado. The Fort Laramie Treaty of 1851 guaranteed ownership
of the area north of the Arkansas River to the Nebraska border to the
Cheyenne and Arapahoe -that part was sighted off history.com- </span>
Protect the US against threats
Answer:
Mississippi River
Explanation:
Much of the commercially important waterways of the United States consist of the Mississippi River System
