Townsend Building address

From: "Glenn G. Willumson" gwillumson@arts.ufl.edu

In his early biography of Carleton Watkins [An early California photographer: C.E. Watkins], Charles Turrill says that the top floor of the 4th and Townsend Building was outfitted for photography. Can anyone tell me what city the 4th and Townsend building was in and what it's purpose was?

—Glenn Willumson