Eriogonum microthecum var. simpsonii and Pediocactus simpsonii, named for Captain James Hervey Simpson, 1813-1883, of the U.S. Army Corps of Engineers, who laid out the Great Basin portion of the modern U.S. Highway 50, participated in a survey of the Southwest.

Silphium astericus var. simpsonii was named for Joseph Herman Simpson, 1841-1918, an American botanist, who collected plants in the United States