If your data was tabular to begin with, consider making that:
- available for download, or
- available for display on the same or another page.
This has the added benefit of sidestepping difficulties with making the map itself functionally accessible, since all the data will be present and digestible elsewhere.
If your map has a ton of elements that can be tabbed through, and also has more content underneath it, consider adding in a skip block.
Skip blocks are normally recommended for elements that are repeated across multiple different pages (i.e nav bars). But in the case of the Chicago Recovery Plan's homepage map, there are 75+ elements to tab through before you can focus on the content below the map. This kind of skip block is more of a nice quality of life feature.