The Space Stone was an incredibly powerful and ancient stone capable of manipulating space. An Infinity Stone, various individuals and organizations have possessed it, including Johann Schmidt, Mar-Vell, Loki, and Thanos.
The first known person to possess the Space Stone was Odin. During the Asgard-Jotunheim War, Odin left the Space Stone, enclosed inside of the Tesseract in Tønsberg, Norway, where it was discovered by Johann Schmidt. Schmidt used the Space Stone to create various bombs and aircraft to attack the United States of America. However, the stone made him the stonekeeper of the Soul Stone, and the Space Stone was left in the ocean until it was found by Howard Stark and later Mar-Vell. While S.H.I.E.L.D. was experimenting with the stone, Loki appeared out of a portal and stole the stone, later using it for the Chitauri invasion.
Following Loki's arrest, the Space Stone remained on Asgard until its destruction in 2017, where it was taken by Loki yet again. During the Attack on the Statesman, Loki gave up the Space Stone to save Thor's life. The Space Stone was ultimately destroyed by Thanos in the wake of the Snap.
In 2023, the Avengers initiated a plan to resurrect the victims of the Snap. Tony Stark was tasked with retrieving the Space Stone from 2012. While Stark was exiting Stark Tower, Hulk rushed out of the elevator, sending Stark flying backwards and the Tesseract insecure, allowing Loki to grab the Tesseract and escape using a portal to the Gobi Desert, creating an alternate timeline. Stark and Steve Rogers time-traveled to 1970, where they visited Camp Lehigh and stole the Tesseract and various Pym Particles.