For most of the sixties, the offices of DC Comics were located at 575 Lexington Avenue in New York…and oh, how I recall that address from putting it on so many letters-to-the-editor I dispatched. I never visited that building. The first time I went to DC was in July of 1970 and by then, they'd moved to larger quarters at 909 Third Avenue. This relocation apparently occurred around the end of 1968 and had to do with not only a need for more space but the corporate acquisition and staff changes around that time.
Todd Klein never set foot in 575 Lexington either. Todd is, of course, the award-winning letterer. In fact, Todd's kind of the Meryl Streep of comic book letterers when it comes to snagging trophies. Anyway, on his blog, Todd has been compiling the memories of others about visiting DC back then and based on what I know, all the reminiscences sound valid except that given the number of editors and other staffers, I suspect the "from memory" floor plans are missing some rooms.
Wanna read this? It's in three parts. Here's a link to Part One, here's a link to Part Two and because I'm a generous guy, I'll even toss in a link to Part Three. Don't say I never gave you anything.