Robert A. Eccleston (1830–1911) was a pioneer, forty-niner, and diarist whose records offer crucial insights into the discovery of the Tucson Cutoff and Yosemite Valley.

[1] Born in New York City to Irish immigrants, Eccleston documented his adventures during the California Gold Rush and the Mariposa Indian War.

The Association traveled by sea to Texas and then purchased wagons for an overland journey with a U. S. Army expedition to establish a military road from San Antonio to El Paso.

The Association then joined with John Coffee Hays and his experienced party of frontiersmen for the journey from El Paso to California.

Robert kept a diary of this journey from April 3, 1849, when they sailed from New York, to December 27, 1849, when they reached the borders of California at Fort Yuma.