Unusual geography puzzle

[Daij]

If you are in Ipswich but according to your map it is only one mile to Chelsea and sixteen miles to Yarmouth, can you tell me why?

[divlong]

Hmm, all three places are in Massachussetts but not that close together.

Ipswich, MA - Chelsea, MA - 26miles
Ipswich, MA - Yarmouth, MA - 103miles