I’ve been going through the past Q&As, and another place to read scripts for free is is the library at the Writers Guild, on Fairfax and 3rd in Los Angeles. While you do have to read the scripts there, it’s a pleasant environment, and the staff is very helpful.
I didn’t even know this library existed, so thanks for writing in. Another great resource is the Margaret Herrick Library on La Cienega, which is run by the Academy. In addition to screenplays, it has clipping files on many topics, and would be the ideal first stop for any research into Hollywood history.