Cocopah II was a stern-wheel paddle steamer (sternwheeler) and the tenth steamboat to operate on the Colorado River. It entered service in 1867 as a replacement for the original Cocopah (often called Cocopah I).
Background and Construction
The original Cocopah, launched in 1859, had been one of the largest and most capable vessels on the river but was taken out of service around 1867. Its engine and boiler were removed, and the hull was hauled ashore at Port Isabel, Sonora (Mexico), to serve as housing for workmen at the port and shipyard.
George A. Johnson & Company (later reorganized as the Colorado Steam Navigation Company in 1869) built the replacement, Cocopah II, at Arizona City (present-day Yuma, Arizona) in March 1867. It was launched there in May 1867. The vessel completed Johnson’s main fleet of four steamers (Cocopah II, Colorado II, Mohave, and Nina Tilden) plus six barges that dominated Colorado River traffic from the late 1860s into the early 1870s.
Captain Isaac Polhamus (also spelled Issac in some accounts), the company’s senior steamboat captain and later known as the “Dean of the Colorado River,” commanded Cocopah II. Polhamus had previously captained earlier vessels such as Colorado I.
Specifications
- Type: Wooden-hulled stern-wheel paddle steamer
- Tonnage: 231 tons (about 3 tons lighter than the original Cocopah)
- Length: 147.5 feet (7.5 feet longer than the original)
- Beam (width): 28 feet (1 foot narrower than the original)
- Draft: Very shallow (sources note under 20 inches when loaded, suited to the Colorado’s sandbars and fluctuating water levels)
- Cargo capacity: Reports vary; one account credits it with carrying about 120 tons of freight on less than 20 inches of water.
These dimensions made it well adapted to the lower Colorado’s difficult conditions of shifting channels, sandbars, snags, and seasonal low water.
Role on the Colorado River
Cocopah II operated primarily on the lower Colorado River, running from the river mouth and delta area near Port Isabel, Sonora (on the Gulf of California), northward past Arizona City/Yuma to landings that served military posts, mining districts, and settlements in present-day Arizona, California, and Nevada. Key stops included Ehrenberg (formerly Mineral City), Aubrey City/Landing (near the Bill Williams River), Hardyville, and Fort Mohave.
It transported freight (supplies, mining machinery, ore, provisions, and general merchandise), passengers, and often towed barges to increase capacity. The boat supported the region’s mining booms (including silver and copper discoveries in areas such as El Dorado Canyon and La Paz), military logistics, and growing settlement. Woodyards along the route—frequently staffed by local Cocopah people—supplied fuel. Crews were diverse and included local Indigenous pilots and deckhands valued for their knowledge of the river’s shifting channels.
One notable performance was a reported record-breaking voyage from Aubrey City to Yuma (about 220 miles) in four days. Other accounts note efficient round trips, such as Yuma to Mohave (roughly 232 miles) in five days under capable captains.
By the late 1860s the company was moving substantial tonnage and earning strong profits. Cocopah II formed part of a fleet that, around 1873, included several steamers and barges making dozens of trips annually as far as Ehrenberg and Hardyville.
Decline and Ultimate Fate
The arrival of the Southern Pacific Railroad transformed the economics of river transport. The railroad reached Yuma, bridged the Colorado River at Fort Yuma around 1877, and purchased the steamboat company. Rail service captured most of the long-haul freight and passenger traffic that had previously relied on the steamboats connecting to ocean vessels at the Gulf of California.
Cocopah II was retired in 1879. It was dismantled in 1881. (Some residual upper-river or local service continued with other vessels for a time, but the classic steamboat era on the lower Colorado effectively ended with the railroad’s dominance.)
Cocopah II exemplifies the peak and relatively rapid decline of Colorado River steamboating: purpose-built shallow-draft sternwheelers that opened the desert Southwest to reliable bulk transport in the mid-19th century, only to be rendered largely obsolete by the transcontinental railroads.