Preheat the oven to 350 degrees F and have ready a 9 inch pie dish.
Process the graham crackers to make 1 ½ cup crumbs. In a food processor (or bowl) mix graham crackers, sugar, cinnamon and butter. Press mixture into and up the sides of the 9 inch pie dish.
Bake on center rack at 350 for 8 to 10 minutes. Remove from oven and let cool for about 30 minutes.
Make the filling. Separate the eggs so that you have 4 yolks and 4 whites , but put aside 2 of the whites because you’ll only be using 2.
Beat the 2 whites until stiff peaks form.
Pour the condensed milk into a mixing bowl. Whisk in the egg yolks, then gradually whisk in the Key lime juice. Fold in the 2 beaten egg whites. Empty the mixture into the graham cracker crust.
Set pie on a baking sheet and bake on center rack for 20 minutes. Let cool at room temperature for about an hour, then chill for 4 hours or until very cold.
Before serving, cover with sweetened whipped cream or pipe it around the edges