In a large bowl, cream together butter and sugar, until light and fluffy.
Beat in the eggs, one at a time, stopping to scrape down the sides and bottom of the bowl between eggs.
In a small bowl, combine flour, cream of tartar, and baking soda.
Add this mixture to the butter mixture and blend just until combined. Over mixing makes cookies tough.
Combine 1/4 cup of sugar with 2 teaspoons of cinnamon in a wide container.
Using a cookie scoop, drop a few rounds of dough into the sugar and cinnamon mixture.
Roll dough rounds until completely coated with sugar and cinnamon.
Place on baking sheet about 2 inches apart.
After half of the dough has been rolled in sugar and cinnamon, add the last teaspoon of cinnamon. This will keep cinnamon in the sugar mixture until all cookies are rolled. If added too soon, you will have too much cinnamon in the beginning and not enough cinnamon at the end.
Continue rolling dough rounds.
Bake cookies at 400°F for 8 to 12 minutes or until edges of cookies are light brown.
Remove from oven.
Allow snickerdoodles to cool on the baking sheet for 1 to 2 minutes.
Remove cookies to a counter lined with aluminum foil or a baking rack. Allow the cookies to cool completely before attempting to stack.
Half of the butter can be replaced with solid shortening.