Note: Updated to highlight search by elected districts.
APTA (American Public Transit Association) makes the APTA Industry Footprint webpage available.
The page provides summaries of transit nationwide industry info, federal appropriations, transit systems, supply chain, facilities, funding, economic impact, spending, and ridership.
A search bar allows subsetting information by state, district, or legislator. For example, you can search by your congressional representative or state legislator. This report by legislator is really the key purpose of the Industry Footprint, to show transit within a particular area served by an elected officer at the federal or state level. The example below is for State Senator Angelique Ashby, District 8. First page as image; full four page report as pdf.

The page also has a data explorer map (scroll to the bottom) which offers demographic data for searchable locations, for example, Sacramento County. It does not appear to offer selection by transit district service area, such as for SacRT or the other transit agencies in the region.
This webpage doesn’t necessarily offer the subset of information you may be looking for, but it is interesting, and of particular interest to transit nerd. There are other sources, which STAR will post on.
