Preheat the oven to 350 °F (175 °C).
In a bowl, combine gingersnap crumbs, granulated sugar, and melted butter until evenly moistened.
Press the mixture firmly into the bottom and slightly up the sides of the 9-inch springform pan.
Bake the crust for 8 to 10 minutes, then allow it to cool while preparing the filling.
In a large bowl, beat softened cream cheese and sugar until smooth and creamy.
Add pumpkin puree and mix until fully combined.
Beat in eggs one at a time, then stir in vanilla extract and all the spices.
Fold in sour cream if using, taking care not to overmix.
Pour the filling over the cooled crust in the springform pan.
Bake for 50 to 60 minutes, until the center is just set but still slightly jiggly.
Turn off the oven, crack the door open, and let the cheesecake cool inside for 1 hour to prevent cracking.
Refrigerate the cheesecake for at least 4 hours or overnight before serving.
Run a knife around the pan edge before releasing the springform, then slice and serve as desired.