Santa Monica Press was established in 1993 and initially focused only on publishing non-fiction with a focus on regional books.
They’ve since expanded, and they now publish within the follow categories:
Biography & Memoir, California, Film, Theater, & TV, Humor, Music, Pop Culture, Reference & Social Sciences, Sports, Travel as well as Young Adult Fiction (Historical Fiction only), and Young Adult Narrative Non-Fiction (both Contemporary and Historical Narrative Non-Fiction).
They are not interested in submissions outside of these categories. Get a good idea for what they’ve published within these categories by browsing their catalogue here.
In the US they are distributed by Publishers Group West, and in Canada their books can be ordered through Publishers Group Canada.
They try to respond to all proposals within two months. They accept proposals via mail or email, although they have separate mailing guidelines for international submissions which you can read as part of their full submission guidelines.
When you submit please include a query letter, a table of contents or outline, two sample paragraphs, sample illustrations or photographs (if applicable), a brief list of similar titles, a marketing/publicity plan or ideas for one, description of your books target audience, biographical information that makes it clear why you are the right author for the proposed book, plus contact info.
Complete submission guidelines are available here, and must be followed closely before submitting.