A native New Yorker, Egleston was the great-grandson of John Paterson, a major general in the Continental Army during the American Revolution.

A graduate of Yale University under the counsel of Dr. Dudley in 1854, he continued his graduate study at Yale and further training in École nationale supérieure des mines de Paris in 1860, after which he was employed by the Smithsonian Museums in Washington D.C.

After leaving Paris, Egleston traveled extensively in France and Germany to study geological collections.

[1] In 1866, Egleston was commissioned to make geological survey of the then developing Union Pacific Railroad and examine fortifications in 1868.

Egleston frequently consulted on metallurgical subject and was a regular advisor for the government on topics of furnace construction and the treatment of ores.