Interruptions, production delays and Bad Company couldn't stop Led Zeppelin from releasing an album that went to number one in the U.S. on preorders alone. Happy Physical Graffiti Day!

It was on this day in 1975 that Led Zeppelin's sixth studio album hit store shelves.

Recording sessions for Physical Graffiti had initially taken place in late 1973 at Headley Grange and the band had used Ronnie Lane's Mobile Studio, but were forced to turn the studio over to Bad Company so they could record their self-titled debut album. John Paul Jones was also exhausted from incessant touring and was looking to leave the group so the band stopped the session, gave up the studio space and Peter Grant told John Paul to take some time off.

When the band reconvened, they immediately laid down eight tracks, the timing of which were too long for a standard album, so the band decided it was better to stretch the record out versus cutting it short and added previously unreleased material to make it a double album. The group added "Bron-Yr-Aur" initially intended for III, "Night Flight" and "Boogie With Stu" initially intended for IV and "Houses of the Holy" that was supposed to be the title track for their previous album all made their way onto Physical Graffiti.

The album cover art is taken from a tenement building at 96-98 St. Mark's Place in New York City's East Village. The structure is actually five stories tall, but the 4th floor was cropped out to make it symmetrical so it would fit on a square album cover. It was tweaked over and over again with railings being removed, windows being added on some of the floors and tiles being added to the roof. The exact artistic nature needed for the front cover, coupled with the intricacies of the inside sleeve design made for more delays in the album's release, but was considered the crown jewel for designer Mike Dowd. (The original jacket consisted of two inner covers, a middle insert and and outer cover. ) It took me a bit to figure it out, but, if you wrap the middle cover around the inner covers and put them into the outer cover, the title of the album shows on the front cover. No wonder it scored a Grammy Award nomination for Best Album Packaging!

Physical Graffiti was both critically and commercially successful. The album was very much a long-awaited release and the huge buildup led to it being the first album to ever get to number one on the U.S. Billboard charts on advance orders alone. It also led to their previous five albums re-entering the Top 200 Chart at the same time.

In case you were wondering, Jimmy Page is credited with naming the album.