The script was originally a true historical incident about a trapper named John Colter being pursued by Blackfoot Indians in Wyoming, but lower shooting costs, tax breaks and material and logistical assistance offered by South Africa convinced Cornel Wilde and the other producers to shoot the film there.

The Man asks the Little Girl if she speaks Swahili, Sesotha, or Zulu. She responds that she speaks Venda - a Bantu language common to northern South Africa and southern Zimbabwe.

Cornel Wilde said in interviews at the time that scene in which his character turns and is narrowly missed by a spear was an accident that could have been gruesomely real, but the scene worked and was kept.

In the commentary track on the DVD, film scholar Stephen Prince reveals that the warrior pursuers speak a Nguni dialect. Nguni is a group of Bantu languages common to southeast Africa.

In October 1808 Colter set out to trap with another member of Lisa's company, John Potts. Foolishly, they returned to the Three Forks area, where they were able to amass almost a ton of fur. However, at Jefferson Fork they were attacked by Blackfeet who shot and killed Potts and took the furs. Colter was captured and given a chance to live. He was stripped naked and given 30 seconds' headstart to run for his life. Colter outran all of them except for one. When they were the only two left, Colter turned upon him and killed the man with his own spear. Colter ran for five miles across a rocky plain between the Jefferson and Madison Forks. Once he reached the Madison River, he dived under a mass of logs and beaver lodges and hid in an air pocket in the icy water until nightfall. He went six miles downstream and climbed up a sheer cliff. He walked, still without any clothes, the 250 miles to Fort Raymond, where he arrived after 11 days.