In regards to your edit, avocados and chili peppers both originate in Mexico. Guacamole was a native dish so it's been around for centuries, but the modern version with onions and cilantro couldn't have existed until the Spanish brought those ingredients to Mexico
Excellent points, but at what time would all of that been written in English and American measurements for American consumers, with ingredients available? I only guessed 1960s, but it very well could have been decades later.
