The dish that's known in the United States as fettuccine Alfredo is just an extra-buttery version of pasta al burro, an Italian classic made with fettuccine, butter, and Parmigiano-Reggiano cheese. The story of fettuccine Alfredo dates back to 1908 in Rome.
Chef Alfredo Di Lelio first created this dish for his pregnant wife out of a desire to create something simple, yet tasty and nutritious, and he subsequently began serving it at his restaurant. He added more butter and cheese to the original recipe for pasta al doppio burro, and created a hearty triple butter sauce in the process.
Soon afterward, fettuccine Alfredo was on its way to becoming an Italian-American classic, and it is incomparably more popular in the United States than in its homeland - it's served in Rome, but usually to tourists, while most Italians don't accept the dish as their own.