Justice Comics was the original super hero comic published by Sentinel Comics. It introduced Paul Parsons VII as the hero Legacy in May 1940 which comics historians consider the beginning of the so-called Golden Age of comics. While other titles came and went over the decades that focused on other heroes, or even Legacy as part of an ensemble, Justice Comics was Legacy's home and solo hero title. That is, until the early 1970s. One of Sentinel Comics' competitors in the business of comic books happened to be named Justice Comics as well, and the legal wrangling that this eventually caused resulted in Sentinel ceasing publication of this title after the December 1971 issue, #380. Legacy found a new home in America's Finest Legacy which began the following month.
This wasn't the end of JC, however. Sentinel Comics eventually resolved the legal snarl by simply buying out their one-time competitor. After this point, they could resume publishing the title, which picked up with issue numbering where they'd left off. Issue #381 was published in February 1987. This didn't result in America's Finest Legacy being cancelled either. While JC continued to be nominally a Legacy book, that role was primarily still held by AFL and JC was, in reality, used as a newcomer-friendly title that had frequent stories featuring other heroes or crossing over with storylines in other titles. If you were new to reading comics, Justice Comics was a good place to start.
Justice Comics continued publication through the end of the "Multiverse Era" of the Sentinel Comics setting, culminating in the OblivAeon event, ending after issue #74X in XXX 2017. This marks it the comics title with the longest period of time between its first and last issues at 76 years and (X?) months. [Note: It's unclear at this time when most comics ended before the line-wide relaunch in the spring of 2017 - if the same month as Freedom Five #803, then JC would have ended with #742 in March 2017, one month shy of 77 years.]
#1 May 1940 - Golden Age begins. First appearance of Paul Parsons VII as Legacy.
#14 June 1941 - First appearance of Corporal Vernon Carter, later reconned as being part of the Ironclad Project and therefore considered a direct predecessor to Bunker.
#20 December 1941 - First appearance of weapons manufacturer Fyodor Ramonat.
#40 August 1943 - Death of Fyodor Ramonat.
#55 November 1944 - Legacy and Vernon Carter team up, implicitly acknowledging that the characters share a setting.
#58 February 1945 - First appearance of Soviet hero Proletariat.
#61 May 1945 - First appearance of Baron Blade (later revealed to be Ivan Ramonat, son of Fyodor), the first use of a "costumed supervillain" rather than the crime lords, weapons manufacturers, or enemy soldiers that were common enemies of the heroes up until this point.
#66 October 1945 - The backstory for the Parsons family and why Legacy is the way he is.
#77 September 1946 - First appearance of Legacy's son, Paul Parsons VIII.
#84 April 1947 - First appearance of The Chairman.
#86 June 1947 - First appearance of Dwight Davis, one of the younger Paul's childhood friends. He reappears as an adult supporting cast member in America's Finest Legacy #114 in 1981.
#101 September 1948 - Death of Legacy at the hands of Baron Blade.
#102 October 1948 - First appearance of Paul Parsons VIII as the new Legacy. First appearance of Emily Evans as Paul's love interest. First appearance of the Soviet villain Iron Curtain. (cover in Hero Challenge document)
#129 January 1951 - First appearance of Black Fist. He goes on to become a regular feature in the backup stories in JC.
#148 August 1952 - First appearance of an official "Bunker" suit.
#182 June 1955 - Birth of Legacy's daughter, Pauline Felicia Parsons.
#243 July 1960 - First appearance of the Wagner Mars Base.
#261 January 1962 - A fight against Grand Warlord Voss crosses over into Freedom Five #141. This is the first multi-title crossover.
#327 July 1967 - First appearance of the Parsons family dog, Spangle.
#380 December 1971 - Last issue before the hiatus. Jefferson Knight, the Director of the Freedom Five Initiative who had just been introduced over in Freedom Five the previous month, arrives to shut things down and reorganize (a meta commentary on the legal situation necessitating the cancellation of this comic).
#381 February 1987 - Return of the Justice Comics title. This occurs during the big Thorathian Invasion story and this issue features Legacy coming out of the coma he'd been in due to events earlier in the arc.
#431 October 1991 - First appearance of Revenant.
#526 March 1999 - "Strike Force Invasion" part 1
#528 May 1999 - "Strike Force Invasion" part 15
#679 December 2011 - "Parsons Family Christmas" before Felicia goes off to college.
#687 August 2012 - Felicia actually leaves for college. Backup stories in JC follow her for a year.
#699 August 2013 - The last of Felicia's backup stories. This coincides with the renaming of America's Finest Legacy to America's Newest Legacy, which becomes her solo title until it ceases publication.
#707 April 2014 - Legacy, Tachyon, and Wraith study an object that will later be named an OblivAeon Shard. This is the first major overt indication that something big is going on.