Historical atlas
Pick a region and a year to see its borders and the states of the time. Every page links to an animated map of the years around it: the same borders, moving.
Europe
The Mediterranean
Middle East & North Africa
Africa
Central Asia
South Asia
East Asia
Southeast Asia
North America
South America
The Americas
The world
Borders: Cliopatria, Seshat Global History Databank (CC BY 4.0). Coarse outlines: check and adjust them for your story.