For the crust combine the crushed graham crackers with melted butter and press into the bottom of a 9 inch spring form pan.
For the filling beat the cream cheese until creamy. Add pumpkin, eggs, sour cream, sugar and spices, beat until combined. Then add the flour and vanilla and beat. Pour the filling over the crust and place the spring form pan onto a foil wrapped cookie sheet. Place in the oven and bake for 15 minutes.
In a medium bowl combine ingredients for the topping. Add the brown sugar, flour and pecans. Cut in the half stick of butter with a knife. After the cake has cooked for fifteen minutes remove from the oven and sprinkle the topping on. Return to the oven and cook for 45 more minutes.
Remove the cheesecake and allow to cool. Cover and place in the oven for at least four hours before serving.