Position a rack in the center of the oven and preheat to 350 degrees . Grease an 8-inch springform pan. In a medium bowl, stir together the gingersnap crumbs, 1/4 cup sugar and the butter. Press the mixture over the bottom and about 1 inch up the sides of the prepared pan. Bake the crust until set, about 10 minutes. Transfer to a rack to cool completely. Increase the oven temperature to 425 degrees .
Meanwhile, using an electric mixer, beat the cream cheese and remaining 3/4 cup sugar on medium-high speed until light and fluffy, about 2 minutes. Scrape down the bowl. Beat in the eggs 1 at a time, beating well after each addition. Add the pumpkin puree, sour cream, vanilla and pumpkin pie spice; beat until combined. Sprinkle the flour over the mixture and beat on low speed until just combined.
Place the springform pan on a baking sheet and pour the filling into the shell. Bake for 15 minutes. Lower the oven temperature to 250 degrees and bake for 1 hour longer. Turn off the oven and let the cheesecake cool in the oven with the door ajar for 2 1/2 hours. Transfer to a rack and let cool to room temperature. Refrigerate uncovered until thoroughly chilled, at least 10 hours or up to 2 days.
Remove the side of the pan and let sit at room temperature for an hour. To serve, cut the cheesecake into wedges with a sharp knife thats been dipped in hot water and wiped clean after each cut. Serve the cheesecake slightly chilled or at room temperature.