Surname distribution maps for Erdman
Erdman in the 1881 Census
Erdman in the 21st Century
The maps, if available, show both where there are more people named Erdman and where they are most concentrated.
The darker the colour, the more people in that county are named Erdman.
The larger the dot, the greater the proportion of people in that county are named Erdman.
Hovering over the dots will give you the individual statistics for that county.