It would definitely be cool to see old highrise/skyscraper buildings get listed as UNESCO world heritage sites.
As far as San Francisco goes, most of its 19th century highrises were destroyed in the 1906 earthquake and fire, but there are a few that survived:
The Central Tower/Call Building/Spreckels building, built in 1898 (315', 15 stories):
On fire after the 1906 earthquake:
Here's how it looks now, after an art deco renovation in 1938 (299', 21 stories):
The Chronicle Building/De Young Building/Ritz Carlton, built in 1890 (218', 10 stories):
It was heavily damaged in the 1906 earthquake, and reconstruction involved the removal of the clocktower, and the addition of a 16 story annex:
It was then covered in an ugly metal skin in the 1960s, which was removed in the 2000s, as part of a project that also added more floors to the building (bringing the height to 312', 24 floors):
The Mills Building, built in 1892 (154', 10 stories):
The Ferry Building, built in 1898 (245'):
