"This is a very old pie, probably invented by people who had little access to fresh supplies such as lemons or cream. Some say that it was the pioneer women who first thought up the idea. The lemon extract in this recipe is a my addition. The original recipe calls for regular vinegar which, for me, gives a bland pie. You can substitute apple cider vinegar, leaving out the lemon extract, for a very good taste. Be sure to let the pie crust cool before filling."