A modern recipe, a little bit different from the 19th century versions.
Compare this recipe for molasses cookies from the July 22, 1873 edition of The Bloomfield (Pennsylvania) Times:
To make excellent Molasses Cookies, take 2 cups of molasses, 2 cups of sour cream, 2 teaspoonfuls of saleratus (put in dry), 2 teaspoonfuls of ginger, and a little salt. Knead just stiff enough to roll out.
You might notice that it doesn’t specify an amount of flour. I’ve noticed that about quite a few recipes from this time period. For example, here’s another recipe for molasses cookies, and one for sugar cookies, from the January 31, 1880 edition of the Dodge City (Kansas) Times:
Hints for the Household
— Molasses Cookies: One cup of molasses, one-half cup of sugar, one-half cup of butter, one teaspoonful each of salt, soda, and ginger. Mix hard.
— Sugar Cookies: Two eggs, two cups of sugar, one-half cup of milk, one cup of butter, one teaspoonful of ginger, and one-half teaspoonful of soda. Mix hard and roll thin.
Or this one, from the August 27, 1800 edition of the Iola (Kansas) Register:
Molasses Cookies — One cupful of molasses, one cupful of sugar, two-thirds cupful of hot water, two-thirds cupful of lard or butter, one egg, one teaspoonful of alum, one teaspoonful of saleratus, and two teaspoonfuls of ginger. These ingredients will make ninety to 110 cookies.
So what’s going on? I don’t know for certain, just yet, but I have a theory. Often, cookbooks of the day would tell you to use enough flour to roll the cookies out, as they did in the 1887 recipe compilation Melrose Household Treasure:
One cup molasses, two-thirds cup shortening, one teaspoon soda, flour to roll as soft as possible. Mrs. C.A. Merrill.
One cup molasses, one cup of butter, one-half cup sugar, one teaspoonful soda dissolved in one-half cup of coffee, one egg, teasponful of ginger. Mrs. S.S. Bugbee.
Even later cookbooks would sometimes give a baseline amount of flour and then tell you to add to it as necessary. For example, this molasses cookies recipe from the 1917 edition of Culinary Echoes From Dixie by Kate Brew Vaughn:
1/2 c. sugar
Mix sugar, molasses and shortening. Add water and 2 cups of flour mixed and sifted with soda, salt and spices. Add enough more flour to roll out. Bake in hot oven.
Until the late 1800s, most flour was stone-ground and wasn’t standardized in any way. Its effect in a recipe would depend on a number of things, including how far apart the stones happen to be set at that mill, the variety of wheat used, and the humidity where it was stored. In the late 1800s, mills started to switch to steel rollers, which provided a much more refined product.
While not knowing how much flour to use in a recipe might feel unusual, if you think about it, we do the same thing all the time with other ingredients. When you make pasta, you have to adjust the flour and water a little each time you make it, because there’s always some variation in the ingredients. (You might well think it would be nice if chickens would lay uniform eggs, but they are disinclined to do so.) When you make potato gnocchi or pumpkin pie from fresh pumpkins, the water content of potatoes and pumpkins varies greatly; you have to just go by instinct, feel, and experience.
From the box of C.C. sold in Ceres, California.
1/2 c. butter
1/2 c. granulated sugar
1/2 c. molasses
1/2 c. sour milk*
1 t. baking soda
2-1/2 c. flour
1/4 t. salt
1/4 t. ground cloves
1 t. cinnamon
1 t. ginger
1/2 c. raisins
Set oven temp. to 350 degrees. Grease cookie sheets. Cream shortening and sugar together. Pour in molasses. Stir.
Add egg to mixture. Stir.
Add baking soda to sour milk in a cup. Stir. Add sour milk to mixture.
Measure flour, salt, and the 3 spices into sifter. Sift. Put sifted ingredients into mixture. Stir slowly. Stir only till flour disappears. Add raisins to mixture.
Spoon batter onto cookie sheet. Cookies stay in a mound. Bake at 350 degrees for 12 minutes.
*If you don’t have sour milk, put 1-1/2 teaspoons of vinegar into glass measuring cup. Pour in enough fresh milk to make 1/2 cup. Let sit for 10 minutes.