Allen Ginsberg also famously spent several months there before that. He had met another well-known Beat, Carl Solomon, in 1949 in a similar facility and would later dedicate "Howl" to him. Lou would become close to Ginsberg and the ex-Beats.
Today I found an expansive site with dozens of photos of the site, equal parts creepy and striking (see note on blackboard), and I will probably takes some pix myself. Read the comments there, some of them quite moving from former patients, though no mention of young Lou. I am researching further on what went on there in 1950s, when Lou was there. For now, here's Ginsberg from "Howl," published possibly same year Lou was there.
Carl Solomon! I’m with you in Rockland
where you’re madder than I am…
where fifty more shocks will never return your
soul to its body again from its pilgrimage to a
cross in the void…
I’m with you in Rockland
in my dreams you walk dripping from a sea-
journey on the highway across America in tears
to the door of my cottage in the Western night
–Allen Ginsberg, (1956)