|First appearance||The Brave and the Bold #28|
|Notable characters||Snapper Carr|
Happy Harbor is a fictional United States location in Rhode Island, referenced in American comic books published by DC Comics. It is the location of the first headquarters, "Mount Justice" or the "Secret Sanctuary", of the Justice League of America, first appearing in The Brave and the Bold #28 (March 1960).
As the home of the Justice League, the city would often become the target of various super-powered beings, such as an invasion by the brainwashing Starro.
This New England municipality was also the home of Snapper Carr and the hideout itself was additionally the setting of the demise of the Doom Patrol team of super-heroes. Later, the facility would be used by other versions of the Justice League, the android superhero Hourman, a new incarnation of the Doom Patrol and, for a time, Young Justice. During the Doom Patrol's second tenure, the city is overcome by perverse sexual impulses due to a supernatural event. The Patrol, with the assistance of extra-dimensional officers, negate the threat, restoring everyone to their right mind.
Secret Origins #32 indicates the mountain cave was located in RI. The cover of Secret Origins #46 shows the blueprints of the Justice League mountain, with an annotated elevation of over 1,000 feet, which would place their base at above the height of the state's actual highest point, Jerimoth Hill.
In the World Without Grownups incident, the town is the focus of an extreme reality altering event, where such things as video game levels and cartoon characters come to life.
In Young Justice #3, Happy Harbor is the focus of a history-altering temporal event. Due to a time-traveling, serious-minded, younger Mister Mxyzptlk, the only outpost of civilized humanity is the city's civic center, crowded with partying teenagers. When Mxy is convinced to assume a life of humor, the world changes back to the way it was, with one exception; Happy Harbor gains a Mxyzptlk-themed amusement park.
In Justice Society of America #34, the JSA temporarily headquarters itself in the Secret Sanctuary. The JLA has loaned the headquarters until the JSA Brownstone is rebuilt.
In Forever Evil #1, the Crime Syndicate meet in Happy Harbor with an army of supervillains in the ruins of the Justice League headquarters. They declare that the Justice League is dead and that the world now belongs to the Crime Syndicate and the Secret Society.
Justice League of America: Rebirth
As of Justice League of America #1 (2017), Batman's new Justice League of America team, composed of him, Lobo, Killer Frost, Atom (Ryan Choi), Ray (Ray Terrill), Black Canary, and Vixen (comics) are based out of Happy Harbor. The former cave headquarters is repurposed into a new headquarters called 'Mount Justice' and introduced to the world. 
In the crossover series 'DC/Young Animals' Happy Harbor becomes ground zero for a reality invasion by the malicious corporation called 'Retconn'. 
In the first few pages of 2006 the D.C./Wildstorm crossover 'Dreamwar', the Wildstorm version of Happy Harbor is destroyed by a tidal wave. It is not a natural event, it is caused by a mentally ill superhuman.
In other media
- Happy Harbor appears at the end of the two-part Young Justice pilot "Independence Day". The Secret Sanctuary is given to the members of Young Justice as their base of operations and it is stated as being the Justice League's original headquarters prior to moving into the Hall of Justice. Happy Harbor is indicated as being in Rhode Island in Young Justice episode "Infiltrator"
- Happy Harbor is mentioned by Nora West-Allen and Flash (Barry Allen) as the location of their favorite dessert in the Season 5 premier of CW’s The Flash entitled “Nora”.