Long before Euro-American settlers arrived, the region surrounding the John Day River was inhabited by Indigenous peoples, including the Northern Paiute and Umatilla tribes, who utilized the river valleys for seasonal fishing, hunting, and gathering.
Euro-American settlement in the Monument area began in the late 19th century, driven by the expansion of cattle ranching and homesteading in eastern Oregon. The town's name was reportedly chosen because of a nearby rock formation that resembles a monument. A post office was officially established here in 1874, solidifying the community's presence on the map.
Throughout the 20th century, Monument operated as a vital commercial and social center for the isolated ranches of northern Grant County. While timber and logging once played a more prominent role in the broader county's economy, Monument itself has primarily remained an agricultural community. Today, it retains much of its historical frontier character, operating as a quiet, remote enclave far removed from the rapid urbanization of the Pacific Northwest.