[1] On November 1, 1850, the Invincible was later sent from San Francisco on a mission to deliver 10,000 rations to the garrison of the remote post of Fort Yuma on the Colorado River.
The Invincible, drawing eight feet of water, was grounded at every ebb tide, which was extreme in the Colorado River Delta.
On January 3, 1850, some 30 miles upriver, Captain Wilcox was forced to drop anchor, his way blocked by shoals too shallow to pass.
Local Cocopah people there that day agreed to carry a message to Fort Yuma of the arrival of the ship.
Arraignments were made to unload the boats at the ship's anchorage on the shore of Sonora and loaded onto wagons from the fort on 28 January.