From the Pier 70: History web site:

"Potrero Point drew the attention of industrialists from the days just after the California Gold Rush because it had cheap land that was isolated from the densely populated city center and because of its natural deep water access.

The geography of Potrero Point and surrounding areas changed drastically over the last 150 years. Industrialists and speculators sought to exploit Potrero Point’s natural advantages and to overcome the obstacle caused by the swampy Mission Bay.

The natural contour of the bay shore was changed by filling, with much of the fill material taken in the process of blasting away the serpentine hills that once rose above the point."