These "big teams" pulled massive wagons hauling borax from the Harmony Borax Works near Furnace Creek to the railhead near Mojave, a grueling 165 mile, ten day trip across primitive roads. Although the teams only ran for six years--1883 to 1889--they have made an enduring impression of the Old West.
This is primarily due to a successful advertising campaign promoting 20-Mule-Team Borax Soap. Today you may see two of the last remaining wagons here in Death Valley. One is in front of the Furnace Creek Ranch and the other is at Harmony Borax Works.