Linked from
The 16 pages that link to Trinity test, each with the reason it gives.
Manhattan ProjectBroader topic: It tested the plutonium implosion design before its use in war.
Hanford SiteRelated: The test device used plutonium produced at Hanford.
Nuclear warfareBroader topic: The test demonstrated the weapon before its use in war.
Nuclear weapon designRelated: The test validated the first full-scale implosion weapon design.
TNT equivalentBroader topic: Its estimated yield is commonly expressed in kilotons of TNT.