Prior to Alviso, the Embarcadero de Santa Clara was functioning as a port.
The Embarcadero de Santa Clara was the site of the first Santa Clara Mission in 1777. In 1779 the Mission moved to higher ground, but the Embarcadero continued as an "embarkment" point for goods shipped from the Santa Clara Valley to San Francisco and beyond.
The Embarcadero de Santa Clara served as a port for the shipment of cow hides, tallow, and other goods marketed by Spanish settlers and the Mission de Santa Clara. In 1835, Richard Henry Dana, author of Two Years Before the Mast, purchased hides from the Mission, loaded them onto a boat at the Embarcadero, and relayed them to his ship in San Francisco Bay.
Some sources state that Alviso was called Embarcadero de Santa Clara before being renamed Alviso . . . close but no cigar. The Embarcadero is located almost a mile up the Guadalupe River from the site of Alivso proper, as indicated on the map. It is a different place.