I’m Writing A Story At The Moment About A Small Small Town That Was Built With Magic.

The town is so small it has only a one room school house, and 179 population. I would like to know what year that the holiday ‘Halloween’ was declared a holiday, because the story shifts between the present time, and 200 years before when it was built, on Halloween. By present time, I mean back when they still used one room school houses. Any help with the Halloween holiday problem would be appreciated!
* If Halloween was declared a holiday only recently (after AD1800) then I suppose I could make some changes *