"Map of White Supremacy mob violence, 1835-1964" is an interactive map created by Monroe Work Today.
From the website:
In the century after the Civil War, as many as 5000 people of colour were murdered by mobs believing the cause of white supremacy.
On average, mobs killed 9 people per month during the 1890s.
The website includes news stories, photos and info about Monroe Nathan Work.
Read more at City Lab.
(Source: Google Maps Mania / Atlantic Cities)
From Keir Clarke:
Under Joseph Stalin the Gulag was the government agency that administered the forced labour camp system in the Soviet Union. The camps were used to hold political prisoners and other convicts. The prisoners lived in terrible conditions and their slave labour was used in industrialization projects.
The Gulag Online Virtual Museum is an interactive map-based portal that includes archival research, oral history and geographical data.
(Source: Google Maps Mania)