Did You Know. . .

that the difference between a blondie and a brownie is that a blondie has a vanilla or butterscotch bar base and that a brownie, of course, has a chocolate base?

that according to old cookbooks, blonde brownies (also known as blondies) came before chocolate brownies, though under different names?  The primary ingredients of blonde brownies (brown sugar/molasses and butter) make butterscotch, a candy that was popular in America in the mid-19th century. Some American cookbooks from that time have recipes that combined traditional butterscotch ingredients with flour and a leavening agent (such as baking powder or baking soda). The presumption is that these recipes would have produced something similar to the blondies we enjoy today.
 
that most likely the beginning of the brownie/blondie recipe goes back even further?   Cookbooks from the European Medieval and Renaissance era have recipes for soft, chewy cakes and cookies that used treacle (a precursor to brown sugar) as an ingredient. It was called gingerbread. Bakers were often instructed to cook gingerbread in shallow pans and add nuts, just like our traditional brownie recipes do today.

that it wasn't until the 1950s that butterscotch or vanilla brownies became known as blonde brownies?