1600s-1700s – The Arapaho were chased from their villages which were believed to be located near the headwaters of the Mississippi River (present day Saskatchewan, Canada). They lost their sedentary corn/maize lifestyle and became nomadic buffalo-hunters. They arrived in the Great Plains and became a dominant trading group.
Mid to Late 1700′s – The Arapaho acquired horses (before European contact). Their women became renowned for their ability to cure the softest hides.
1780 – The Arapaho population is estimated to be 3,000
Late 1700′s – Soon after their first contact with the Europeans, the Arapahoes split – the Northern Arapaho settled in Eastern Wyoming and the Southern Arapaho settled in Colorado. (They continued to be allies but this division occurred when the European settlers blazed a path through the middle of their mutual grounds which split the buffalo herd they depended on into two herds. The Lakota Sioux and Cheyenne had signed a friendly treaty that allowed these wagon trains to pass through their territory unmolested.)
1834 – The Fort Laramie Trading Post was established at the Laramie and North Platte Rivers in modern day southeastern Wyoming, the heart of the Arapaho hunting grounds. It quickly became the most popular trading post on the Central Plains.
1836 – The Fort Laramie Trading Post was purchased by the American Fur Company which called the region “beaver trappers paradise”. The Northern Arapaho set up camp near the post to participate in the flourishing fur trade.
1843 – The Great Oregon migration brought thousands of settlers through the territory and the fur trade was virtually abandoned as the trading post became a refuge and stop along the way for these travelers.
1849 – The U.S. Government purchased the trading post and created a military post designed to protect the settlers traveling through Indian country. The Arapaho, Cheyenne and Lakota Sioux were no longer welcome after years of interacting with white traders.
1851 – A temporary intertribal truce was called and 10,000 Native Americans gathered 20 miles east of Fort Laramie to negotiate a treaty with General Harney.
Mid-1850′s – The Fort Laramie Treaty of 1851 proved ineffectual and was broken by both Native Americans who were unaware of the treaty and the federal government who ignored settlers claiming the land promised to the tribes.
Late 1850′s – The Arapaho, Comanche, Cheyenne and several other bands formed “The Alliance” and took control of much of the Plains. This time period was known as “The Great Peace” and the Alliance was able to provide their own brand of justice since the military was occupied with the Civil War.
1864 – General Chivington attacked a peaceful Cheyenne village and their allies, the Arapaho. The Sandcreek Massacre became known as a brutal assault on mainly elders, woman and children. It was one of the last civil war “battles”.
July 1867 – The U.S. Congress began the “General Peace Policy” to “abolish Indian wars forever by removing their causes.” The goal was to convince tribal people to give up their nomadic hunting lifestyle and take up farming so that they would stop attacking the railroad and frontier settlements.
1867 – The Arapaho and their allies signed the “Medicine Lodge Treaty” at Medicine Lodge Creek in southern Kansas. The Arapaho and Cheyenne wee granted lands that would constitute the Cheyenne and Arapaho Indian Reservation.
November 1867 – Despite the treaty, General Custer and his men attacked the close Arapaho allies, Black Kettle’s band of Cheyenne, in the Battle of Washita (near present day Cheyenne, Wyoming).
Nov-Dec 1867 – The “Red River War” military campaign was launched to round up the remaining Arapaho, Comanche, Kiowa and Southern Cheyenne and place them on reservations.
1875 – The last renegade band of free Arapaho surrendered.
Today, the Northern Arapaho live in Wyoming on the Wind River Reservation they share with the Shoshone and the Southern Arapaho are in Oklahoma with their Cheyenne allies.
For more information and a quick read, I recommend “Native American Tribes: The History and Culture of the Arapaho” by Charles River Editors