Some excerpts from the article written by Dana Bowen:
The earliest printed recipe for brownies dates to 1896, when the first edition of Fannie Farmer's seminal Boston Cooking-School Cookbook was published. The recipe in that book yielded a dessert that didn't look or taste at all like today's brownies . . .
By the time the Betty Crocker company introduced its first brownie mix in 1954, Joy of Cooking contained four very different brownie recipes. Though I gave up on store-bought mixes when I realized I could make better brownies just as effortlessly from scratch, I confess that some of my earliest lessons were gleaned from the back of a box: add an extra egg for cakier brownies; use less fat for fudgier ones.