The little blue house with white trim tells a story. The builders paid for fancy window trim and an ornate cornice, so it was probably built after the Silver Rush of 1859, which brought San Francisco even more wealth than the Gold Rush of 1849. All that wealth allowed people to build more impressive homes and custom wood-working shops opened to supply the need.
But the original owners did not pay for bay windows. Maybe that's because so much of the front is glass. Bay windows might have looked like they were crowding each other. Plus it's a small house, as you can see from that side wall. It's only a little deeper than it is wide. And the cornice is a false front. It makes the house look bigger than it really is.
The new white house next door is taller, wider and deeper than its little neighbor from the days of the Wild West. It's possible two little old houses like the blue on were torn down to make room for it. It really is as big as it looks.