I was using the 1970 block data for a project and it’s been great. I have been unable to locate any block maps for 1970 anywhere. Do you have a recommendations on how I can understand the block data I am analyzing? I am looking specifically at San Francisco County.
We don’t know of an existing general source of digital maps of 1970 block boundaries. The Census Bureau published a series of print volumes of 1970 block data that include maps. Many university libraries have copies of those volumes.
As it happens, though, we’ve already started on a project to create 1970 block boundary data for NHGIS, and we’re on track to publish our first release sometime this fall. Serendipitously, San Francisco is one of a handful of areas that we’ve already completed. We can share the data for San Francisco County in a preliminary file very soon; it just needs a couple finishing touches. I’ll report back here with a link when it’s ready, possibly early next week if not later today.