The first major wagon train heading for the Pacific Northwest sets out on the Oregon Trail from Elm Grove, Missouri, with 100 pioneers.

A wagon train is a group of wagons traveling together. Before the extensive use of military vehicles, baggage trains followed an army with supplies and ammunition.

The Pacific Northwest (PNW) is a geographic region in Western North America bounded by its coastal waters of the Pacific Ocean to the west and, loosely, by the Rocky Mountains to the east. Though no official boundary exists, the most common conception includes the U.S. states of Oregon, Washington, Idaho, and the Canadian province of British Columbia. Some broader conceptions reach north into Alaska and Yukon, south into Northern California, and east into western Montana. Other conceptions may be limited to the coastal areas west of the Cascade and Coast mountains.

The Oregon Trail was a 2,170-mile (3,490 km) east–west, large-wheeled wagon route and emigrant trail in North America that connected the Missouri River to valleys in Oregon Territory. The eastern part of the Oregon Trail crossed what is now the states of Kansas, Nebraska, and Wyoming. The western half crossed the current states of Idaho and Oregon.

May 16 is the 136th day of the year in the Gregorian calendar; 229 days remain until the end of the year.