(Most of these are thanks to Rebecca Onion of SLATE)
Mapping Inequality - Redlining Data and Maps from 1930s about neighborhoods (including LA) and what were considered a good loan risk. .
Six degrees of Sir Francis Bacon - network of connections in European intellectuals circa 1600
Colored Conventions (coloredconventions.org) - Data about Black political organization in the 1800's
Histography (https://histography.io/) - an interactive timeline of all historical events on Wikipedia.
Los Angeles Census Data 1940 Maps by ethnicity (UCLA Library collection)