Show HN: BlockAtlas – a very detailed interactive map of US Population Density

The US Census publishes block-by-block population & housing data[1], and I couldn't find an online map of this, so I built one. It also includes lots (10k+) of other indicators published from the Census' annual survey, aggregated to larger levels.

Some queries that should work:

- A zip code (should be fastest, shows block-by-block population density)

- An address (block-level population density within the surrounding zip code)

- A demographic/population/housing indicator (e.g. "$500k+ homes", "percent of people who drive to work" - shows US States and you can double-click to see more detail)

- A comparison between two indicators (e.g. "median income vs homeownership rate") - this shows two maps which zoom & pan together

You can also try to search for an indicator and a place, e.g. "population density by zip code in Los Angeles County" - this only works sometimes though, I'd like to made it more reliable.

Searching these demographic indicators is tricky and I haven't totally solved it, but I think this works reasonably well. The search backend uses LLMs for query parsing, result selection, & embeddings, and uses postgres full text search + pgvector for retrieval. The app is hosted on CloudFlare Workers and mostly written in TypeScript.

I posted this as a Show HN about a month ago, but am posting again because I've made some pretty substantial changes since then (block-by-block data and comparisons are new).

[1] Specifically, population and occupied/vacant/total housing unit counts, with some randomness added by the Census for privacy