The picture is on the corner of Gold Street and Sansome. Looking west from that corner, back into Gold Street, you can see what a nondescript place it is now. But during the Gold Rush days, the first assaying office was opened on this street. In fact, in that picture of Gold Street, if you look closely, you'll see a vertical black store sign "BIX". BIX is in an old assay office. A better photo can be seen here; this picture shows Gold Street from the other end. It was on this street and a perpendicular alley named Balance that all the gold assaying was done when the miners came down from the gold fields.
While "Gold" street is self-evident, do you wonder why the alley was named "Balance"? Nothing to do with weights and measures! The ship named "The Balance" is buried beneath the corner of Jackson and Balance Streets.
Everything on the north side (on the right side of the picture) was rebuilt after the 1906 Earthquake and Fire, but the look-and-feel of the street remains very much Gold Rush.