The link below lists all SF municipal websites that provide public datasets related to property. I do not know if any of these datasets have ownership records.
I just found some more information from the city website sf311:
Assessor-Recorder - Owner of Property in San ...
Doubt you'll find it all in one place, without visiting a city office, but here's some help:
City Lots shapefiles
San Francisco Housing Authority Lots
Now you have all of the ...
Census of Agriculture (Ag Census) has this data, but you are going to have to put it together.
It goes down to FIPS Code level, so basically localities, and you'll need County Level data, plus the shapefiles.
https://earthexplorer.usgs.gov has various types of data worldwide. One of the categories is land cover. Use the interactive map tool to check if the data you want is available for your area of interest.
I have used the following sources in the past for volcano data:
Global Volcano Locations Database from data.gov
Volcano - Population Exposure Index(GVM) from humdata.org
Unfortunately I do not know if the coverage would be sufficient for your purposes.
Land Cover Institute (Global)
North American Land Cover Data Links - Land Cover Institute
Geospatial Data: Land Cover & Land Use of Canada
Natural Resources Canada
Characterization and Monitoring Change of Canada’s Land Surface
"Land Cover" Search Results - Natural Resources Canada
Land Cover and Vegetation - Natural Resources Canada
Have you checked this out ? http://earthexplorer.usgs.gov/
Late answer, but may be of help to those who come after.
Contaminated land data is collated by the improvement service on their 'spatial hub'. It is not open data, but it can be previewed, by clicking on 'preview' here.