In the fall of 1863, the Eureka Mining District was formed when silver strikes were made in the Chocolate Mountains of Arizona. Eureka Landing and Williamsport grew serving these new mines in the district. The landings and mining district appear in the 1865 Map of the new Arizona Territory. Eureka was a small cluster of adobe buildings on the riverbank, 47 miles up river from Arizona City and 2 miles up river from Eureka Landing. Across the Colorado River was Picacho, California and the Picacho Mining District.[1]: 40, 64, 167