The large white Y on the side of the mountain has become the nationally recognized insignia for BYU and the reason why BYU is often called "the Y". It was first built in 1906 using rock and lime, and as since been made more permanent with the additions of concrete and paint. At 380 feet long and 130 feet wide, the Y is larger than the letters of the Hollywood Sign in Los Angeles.

Although Y Mountain does not have the elevation of nearby neighbors like Mount Timpanogos, Cascade Mountain, and Provo Peak, it is one of the most recognizable mountains in the Provo/Orem area. The concrete block Y is the symbol of Brigham Young University ("BYU"), and was supposed to be the center of a giant BYU at one time. But only the Y made it to completion, and the mountain got named. Notwithstanding its somewhat artificial name, Y Mountain towers 4,000 feet over Utah Valley.