MS is very common in Western New York… home of Love Canal and plenty of less-publicized toxic dumping.
Apparently Syracuse is the chart-topper: https://cnycentral.com/news/local/the-ms-mystery-in-syracuse-why-do-we-have-highest-rate-of-multiple-sclerosis-nationwide
Old data (2010), but the 7th page of this pdf shows the northeast generally highest US-wide: https://n.neurology.org/content/neurology/92/10/e1029.full.pdf
"Old data" because a 2019 study doubled the estimate of people living with MS: https://www.nationalmssociety.org/About-the-Society/MS-Prevalence