Early explores often followed other river courses or existing pre-contact trails. Most of the West is filled with reasonably-plentiful sources of water - keep in mind that the West, the largest region of North America, is represented by extremely diverse environments. The stereotype of the Great American Desert is overplayed and inspired by the arid Southwest and/or the large swaths of dry land in the Northern Great Basin. In the latter, the Humboldt River and other rivers (often little more than creeks) provided paths to traverse the region.

In the Southwest, there were well-established trails that necessarily lead from one source of water to the next. What became known as the Mormon or Spanish Trail led through what the Spanish called Las Vegas, referring to the well-watered valley with its source of water, a natural spring that yielded enough water for a sizable settlement even before the construction of Hoover Dam. The trail allowed for a weary traveler to make it from one watering hole to the next without succumbing to even this most inhospitable of Western environments.