CROSSING THE Great Plains The was an overland emigrant route in the United States from the Missouri River to the Columbia River country, was the way to travel back in the 1840’s through the 1860’s. In 1843 the "Great Emigration" began and the west would never be the same after the out set of the travelers. The pioneers by wagon train did not, however, follow any single narrow route. In open country the different trains might spread out over a large area, only to converge again for river crossings, mountain passes. In time many a ....