The earliest-documented advertisement for a Tuesday taco special I could find is in the classified section of the October 16, 1933, edition of the El Paso Herald-Post. Under the headline "Some Good Things to Remember," the White Star Cafeteria at the St. Regis launched a weeklong campaign to let everyone know it sold "Mexican Tacos" on Tuesday -- three for just 15 cents.
Newspaper clippings from across the country showed restaurants offered Tuesday taco specials in the ensuing decades, sometimes coming deliciously close to using “Taco Tuesday.” Albuquerque’s Zia Lounge gave away free tacos on Tuesday in early 1949. Around the same time, Oliver’s in Green Bay, Wisconsin, featured a Tuesday taco deal -- free coffee with every purchase. A restaurant called La Cucaracha declared tacos were their “Tuesday special” in the April 13, 1965, edition of the Minneapolis Star Tribune; a small ad in the January 31, 1967, Arizona Daily Star asked readers to "Stop at Pinky's for Tacos"; the next line said, “Tuesday, 6 for 98 cents.” And Combe's Dining Parlor told readers of the Ogden Standard-Examiner in Utah to “Try our Tasty Tacos Tonight” on March 5, 1968 -- a Tuesday.
But the first true documented use of “Taco Tuesday” appeared in the August 20, 1973, edition of the Rapid City Journal in South Dakota. Under the drawing of a Spanish flamenco dancer, the Snow White Drive In asked people to “Stop in on Taco Tuesday.” The Spanish motif continued in Manhattan, Kansas, two years later, where a restaurant called Marti's announced “Every Tuesday is Taco Tuesdays,” complete with a drawing of a bullfighter. “Crisp shell, tangy meat, lettuce, cheese and sauce make our tacos always a treat,” read the ad in the Manhattan Mercury. Cost? Nineteen cents for one.