A Google search yields no answer to your first question, however, I did learn a new factoid - Allentown is apparently credited for the first ever Halloween parade here in the US.I am not originally from the Lehigh Valley.
Why does the Lehigh Valley celebrate Halloween on nights other than Halloween?
Does anyone really know the reason for this?
Of the 6 states and numerious cities I have lived in, I have never heard of this until I moved here.
This year I am putting up a sign in my front yard that reads:
"Celebrate Halloween on Halloween"
According to my mom, the origins with the Friday trick-or-treating started with teachers complaining that kids were coming to school tired when Halloween fell on school nights.
Since then, it's been tradition. As far as I know, it's been like this my whole life (I'm 26).