If I am right, this is the first time we encounter the term "heliograph transparency" at Shorpy's.
In the "Printmaking dictionary" you may find some explanations for the term, but, to be honest, it doesn't really make me wiser as what a heliograph transparency could be, although one of the explanations mentions a "reproductive process using a transparent support."

Wood sidewalks are not a San Francisco phenomenon based on slopes, they were pretty universal in 1880 and mostly used until 1900. Concrete and concrete construction improved after 1880 but were mostly focused on getting steel reinforcement improvements for construction. However a few concrete sidewalks existed by 1860.

Two possible explanations for the wood-plank sidewalks:

1. Wood was cheap and plentiful in San Francisco in the 1880s, before we chopped down the old-growth forests.

2. As someone who used to work in a factory where we poured concrete, I would say that pouring concrete sidewalks would definitely be a challenge on those steep San Francisco hills. The wet concrete would flow down the hill before it cured unless it was mixed very dry and salted with lime to promote faster curing. But those techniques tend to weaken the concrete. I don't know how they do it nowadays. Some steep San Francisco sidewalks are actually molded as steps!

The place is built of wood, and the blocks you see that make it resemble a stone structure are known as quoins. Often seen on even simple buildings, and many stucco structures have similar. San Francisco had way more wooden buildings than masonry- in fact one of the biggest imports to the city was lumber, down to whole 'rafts' of it floated from up the coast. Try that with stone sometime!

I think the building is made of wood, but made to look like stone.

While raised wooden sidewalks were common in the west during this period, the cobbled streets, gas lamps and stone building in this image makes the (apparently) wood planks of the sidewalk seem out of place. Any urban pavement historians out there?