In 1906, the Junior Class of 1907 whitewashed their graduation year on the mountain east of campus, provoking a clash with the Senior Class until the numbers were finally obliterated. To prevent further conflict, President Brimhall approved a survey of the letters B, Y, and U on the mountainside by Ernest Partridge and students Elmer Jacobs, Clarence Jacobs, and Harvey Fletcher. At the first Y-day, the student body formed a long human chain up the hill to carry lime, sand, and rocks, but after a day of exhausting labor only the Y was thinly covered, and the other two letters were abandoned. Students then repeatedly repaired the fragile lime-powder letter, added a layer of rock in 1908, and added blocks or serifs in 1910 or 1911, creating the block Y recognized today. For years, freshmen, sophomores, juniors, seniors, faculty, and the band all played assigned roles in annual Y-day work, which involved clearing brush, hauling water, mixing whitewash, and coating the letter with large quantities of salt, lime, and water. That tradition lasted until 1972, when helicopters began carrying whitewash up the mountain to reduce environmental damage from the yearly bucket brigade. In 1978, the face of the Y was coated with gunite made from sand, white cement, and water, ending the need for annual whitewashings, and the letter is now repainted every 2-5 years as needed. First lit in 1923 to burn back overgrown vegetation, the Y evolved from pitch-soaked cotton bales or mattress stuffing to electric illumination, and in 2016 the university acquired associated property and access trail land from the federal government, added permanent power, lighting, and trail improvements, and made it possible to light the Y electronically from campus. The illuminated Y greets Utah Valley, is lit on special occasions, and marks both the arrival of new students and the graduation of seniors.