Question

"down the ohio up the mississippi and westward on the missouri river" describes the principal route of which group

Answer 1

The correct answer to this open question is the following.

"Down Ohio up the Mississippi and westward on the Missouri River" describes the principal route of the Seneca and Shawnee.

The Shawnee Indian tribe lived in the area of the Ohio River, but when the Indian Removal Act was enacted in 1830, they had to relocate to the western territories of the Mississippi River, where they intermingle with the Seneca Native American Indian tribe. In December 1932, both tribes signed a cooperation agreement called "the United Nation of Seneca and Shawnee," and settled the Indian Territory of what today is Oklahoma.

Answer 2

The correct answer is: The Shawnee and the Senecas.

According to Wikipedia:  

“The Shawnee are an Algonquian-speaking ethnic group indigenous to North America. In colonial times they were a semi-migratory Native American nation, primarily inhabiting areas of the Ohio Valley, extending from what became Ohio and Kentucky eastward to West Virginia, Virginia, Pennsylvania, and Western Maryland; south to Alabama and South Carolina; and westward to Indiana, and Illinois.”

“Senecas are a group of indigenous Iroquoian-speaking people native to North America who historically lived south of Lake Ontario. They were the nation located farthest to the west within the Six Nations or Iroquois League (Haudenosaunee) in New York before the American Revolution.”