3/22/1975: Led Zeppelin were enjoying a six-week run at No.1 on the U.S. album chart with Physical Graffiti, the group’s fourth U.S. No.1 album. On its first day of release in the U.S. the album shipped a million copies – no other album in the history of Atlantic records had generated so many sales. Physical Graffiti has now been certified 16 times Platinum by the Recording Industry Association of America (RIAA) for US sales in excess of 16 million copies.