Preheat oven to 350°F Line two 9x4" baking sheets with parchment paper and set aside.
Measure flour, cinnamon, baking soda, and salt into a small mixing bowl and stir together; set aside. In a medium bowl, beat eggs, sugar, molasses, and vanilla until smooth. Add dry ingredients a little at a time, mixing well after each addition to a stiff dough. Divide in half. Flatten each half to 1/2" rectangle on baking sheet.
Bake 30 minutes; cool slightly. Cut into 1/2" slices and arrange cut sides down on baking sheet. Reduce heat to 200F and bake for 15 minutes. Turn and bake 15 minutes more. Cool completely.