Preheat oven to 425 degrees
Mix sugar, flour, salt & cinnamon (if using) and sprinkle over blueberries.
Line plate with one pie crust, Pour berry mixture into crust, and dot with butter.
Cut remaining pastry ½ – ¾ inch wide strips to make lattice top, crimp & flute edges.
Bake pie on lower rack of oven for about 50 min, or until crust is golden brown.