Added for the sake of completeness:

Willis et al. have written another paper on the geographical prevalence of PD in the US. They find [1]:

"We identified 27,538,023 Medicare beneficiaries that met our inclusion criteria, of whom 392,214 had a PD diagnosis in 2014. ... Crude prevalence varied from 845/100,000 in Minnesota to 1781/100,000 in New York. The top five states—New York, Connecticut, Florida, Pennsylvania, and Rhode Island—contained 20.7% of all Medicare beneficiaries diagnosed with PD in our sample. After adjusting for baseline differences in race, age, and sex, New York, Illinois, Connecticut, Florida, Pennsylvania, and Rhode Island remained the states with the highest prevalence."

Reference:

[1] "State-level prevalence, health service use, and spending vary widely among Medicare beneficiaries with Parkinson disease"
Sneha Mantri, Michelle E. Fullard, James Beck & Allison W. Willis
npj Parkinson's Disease 5, Article number: 1 (2019)
State-level prevalence, health service use, and spending vary widely among Medicare beneficiaries with Parkinson disease | npj Parkinson'''s Disease

John