Avengers Mansion first appears in Avengers #2 (Nov. 1963)
When occupied, the mansion was originally the Stark family manor, until their only son, Tony Stark, inherited their fortune and soon took on the guise of Iron Man. He donated the mansion to the Avengers and had it financed through the charitable Maria Stark Foundation. It was primarily looked after by the Stark family butler, Edwin Jarvis, who not only took care of the mansion but also catered to the needs of the Avengers team. It served as a place to plan and strategize and a home for Avengers members when they needed it.
It had three above-ground floors and three basement floors. The first three floors were open to the public and had twelve rooms to house Avengers who wished to reside in the mansion, as well as Jarvis's quarters. A portion of the mansion's third floor served as a hangar for the Avengers' quinjets, their primary mode of transportation.
The three floors below ground were restricted from the public and had modified rooms for the Avengers' needs. Such rooms below ground were: Howard Stark's "Arsenal" chamber, the Avengers gym, Hawkeye's test-shooting room, the training room (much like the X-Mansion's Danger Room), the cryogenic storage area, a vault to contain Jack of Hearts's power, and the ultra-secure assembly room.
The Fantastic Four took up temporary residence at Avengers Mansion after their headquarters (the original Baxter Building) was destroyed.
The mansion has been destroyed twice. The first time was in Avengers: Under Siege when a huge grouping of Masters of Evil, led by Baron Helmut Zemo, attacked the Avengers and destroyed the Mansion and beat Hercules into a coma among other things before being repulsed. In the immediate aftermath, the Avengers would relocate to a floating platform called Hydro-Base, while the former Mansion site became known as "Avengers Park", and was unused. Hydro-Base was later destroyed as well.
The Mansion would be featured in a Damage Control story. The reconstruction firm was hired to refit and rebuild the mansion, a task they accomplished easily. Unfortunately they did not manage to move it as easily and it fell into one of New York's rivers.
Later, the Avengers built a new headquarters on the site of the Mansion and resided there until it was destroyed by the Gatherers, a team of alternate universe Avengers. Ute, a Watcher enslaved by the villain Proctor, brought an alternate reality version of the original Avengers Mansion to the site as a dying gift. This replacement Mansion would survive various assaults until, in the "Avengers Disassembled" storyline, the Scarlet Witch was responsible for its destruction by bringing an undead version of Jack of Hearts that exploded, also killing Scott Lang, the second Ant-Man, and in Avengers Finale (January 2005), Stark decided that with his dwindling assets, he could no longer afford to maintain the building and it was abandoned in its derelict state, left as a memorial to the Avengers who had died. Stark, using his considerable political and social influence, had the grounds declared a landmark by the city of New York. Since then, the Young Avengers have restored much of the statuary on the grounds of the mansion. The Avengers have relocated to Stark Tower, although it is unknown how permanent this move will be, especially in light of the events of Marvel's Civil War storyline, which causes the virtual splitting of the New Avengers down the line between those who were pro-registration and those who were against it. Even after its destruction, the mansion remains a hub of superhuman activity. The Young Avengers were attacked by, and later defeated, Kang the Conqueror there. They later restored the many statues in the mansion's grounds, adopting the mansion as their meeting place.
During the highest tensions of the Civil War incident, Iron Man and Captain America meet at the ruins in order to talk things out. They tour the grounds and even find abandoned framed photographs of old allies.
Former Avenger Clint Barton has made his way on to the grounds several times since then, most recently following Captain America's death. He meets with Tony Stark to discuss the implications of Steve Rogers' assassination. After the Skrull invasion, [Agents of S.H.I.E.L.D.](series:722469)'s replacement agency H.A.M.M.E.R. kept an eye on the mansion in case the Young Avengers, still wanted for refusing to be registered, showed up. The young group did anyway, using the building as a central point for many meetings.
Following the Siege of Asgard and at the start of the Heroic Age, Steve Rogers and Tony Stark sold the mansion to Luke Cage for a dollar allowing him freedom to recruit his own Avengers team and operate from the mansion while the other Avengers team operate from the Infinite Avengers Mansion and Avengers Tower. After an extended period, the New Avengers dissolve, and Cage sells the mansion back to Stark.
After yet another roster reshuffling, the mansion is refitted as the headquarters for the new Avengers Unity Squad which is funded by Janet Van Dyne. A computerized A.I. system called J.A.R.V.I.S. is installed to replace Edwin Jarvis (who still lives in Avengers Tower with the main team).