Marvel started writing superhero stories for teens and college students in the 60s. When did DC start aiming at teens and young adults?
The original Teen Titans series from 1966 was probably intended for teens, as were any number of Bronze Age titles. The New Teen Titans series from 1980 was certainly targeted toward teens, to much success. The 1980s also saw comics that dropped the CCA endorsement and directly targeted mature readers (such as Swamp Thing), and around that same time, direct market issues began boasting on their covers, “DC comics aren’t just for kids!”
At least a few issues edited by Julie Schwartz was geared to older readers who knew the Golden Age heroes.
Flash featuring Original Flash Jay Garrick
Also other Showcase and Brave and Bold Team Ups like
Dr Faye and Hourman
Black Canary and Starman.
I think Hawkman was more for adults. Perhaps that is why it had a hard time staying published.
Also Adam Strange in Strange Adventures has a Buck.Rogers / Flash Gordon comic strip, not comic book feel to it.
The storyline I always think of is the Green Lantern/ Green Arrow Hard Traveling‘ Heroes run from 1970-1971. Written by the incredible Denny O’ Neil with art from Neal Adams. The Neal Adams art alone is with reading these stories. The story has Green Lantern and Green Arrow traveling across America taking on contemporary issues and attempting to define what the meaning of being a hero is.
The Bronze Age, early ‘70s. The idea in the Golden Age and early Silver age was that once readers hit puberty they would stop reading and find another hobby and a new generation would cycle in. The Silver Age is when that stopped happening and readers instead stayed on board into their high school and college years. You can see the response to this in Marvel Comics from the era. The storytelling becomes much more serialized and mature. DC was a little late to the party, however. Their movement into the young adult-oriented field started more as a response to Marvel as opposed to a response to reader demand.