The Library of Congress Subject Headings for LGBT-related material are quite general. Most material is classed under homosexuality, lesbianism or transgender with various subheadings.
LCSH has a responsibility to reflect the naming of ideas as understanding and descriptive language is evolving and in transition, and occasionally lags behind current usage. This can cause inconsistency, overlap and archaic terminology in subject headings, especially those concerning cultural identity. For example, the subject headings transgender and transexual are both used, and the distinction isn't clear.
A useful subject heading for historical overviews, etc.:
- Gay liberation movement -- United States -- History
You'll probably have more success with keyword searches using transgender* or gay or lesbian* or queer* in combination with other terms. Keyword searches include tables of contents as well as titles, which is especially helpful for tracking down edited anthologies and other multifaceted material. You can also sort by year to bring more recent or older published material to the surface.
Ending a word stem with an asterisk enables you to find all words beginning with those letters. For example, psych*= psychology, psychologist, psychiatry, etc.
Once you find a good source, you can use its bibliography to branch out and find more related material.