Solar power's impact on the American west will be larger than the mere footprints of the plants in the Mojave.
As the railroads shaped the American West in the 19th century and the national highway system shaped the region in the 20th century, a new electrical generating and transmission system for the 21st century will leave a lasting mark on the desert, for better and worse. Much of the real significance of railroads and highways is not in their direct physical impact on the landscape, but in the ways that they affect the surrounding landscape and communities. The same is true of big solar and wind generating plants and the power lines that will be laid down to move electricity around.
Look at any map of the West that shows land ownership patterns and you will see what I mean about the railroads. Instead of just a thin pair of tracks, the railroads have left a wide swath of "checkerboard lands" through the territory. For 20 miles on each side of the railroad, companies were granted alternating square sections of land. In much of the West, the other squares have remained public land. Some of the railroad sections were developed, others remain undeveloped, and in both cases the crazy quilt of landownership has presented daunting challenges for land management to this day. Poke around towns along the interstate highway system in the West and you'll find old abandoned town centers that lost their lifeblood as the railroad station was displaced as the heart of the town by a new highway. Later that strip was abandoned when an interstate exit became the key connection to the arteries of the region. More than a few towns lost their souls in the process.