El Dorado was a 2 kg side-wheel steamship, was ordered by Captain J. W. Wright and built by Thomas Collyer. It was originally to be named Caribbean; however she was sold while still on the stocks to Howland & Aspinwall, who were building up a fleet of steamers on the Atlantic Ocean. [1]: 201 [2]: 42, 43 [3]: 133, 135 [4]: 336 [5]
By that spring the El Dorado had been switched to the run to Stockton, making connections with the Captain Sutter which was put on the run up the San Joaquin River to Grayson City and the Tuolumne River to Tuolumne City with the Georgiana.[7] The steamer Captain Sutter was run daily on this route until June 1850, when she was sent to run in the Sacramento River above Sacramento.[8]: 85, 86
Faced with the mushrooming numbers of steamers appearing on all the rivers, the Aspinwall Steam Transportation Line offered the El Dorado, Captain Sutter, its other steamboats and its other boats and barges for sale from November 1850.[9]
El Dorado was purchased by June 1851 by the San Francisco Towboat Company run by James Blair, formerly manager of the Aspinwall Line in San Francisco. El Dorado and steam tugs Firefly and Redding were used for towing ships in San Francisco Bay, "to the heads at all times or to any part of the bay and harbor."[10]
^Daily Alta California, Volume 1, Number 127, 27 May 1850
^Tinkham, George H., History of San Joaquin County, California: with biographical sketches of leading men and women of the county who have been identified with its growth and development from the early days to the present, Historic Record Company, Los Angeles, California, 1923
^Daily Alta California, Volume 1, Number 296, 24 November 1850 P.1 Col. 1
^Daily Alta California, Volume 2, Number 181, 9 June 1851, P1C2 SAN FRANCISCO TOWBOAT COMPANY. Steamer EL DORADO; steam tug FIREFLY, steam tug REDDING. Ship, towed to the heads at all times or to any part of the bay and harbor. Orders left at the office of JAMES BLAIR, Agent, Corner Sacramento and Front sts.