I can't verify this any more because I spiked my Nextdoor account by "moving" to Comiskey Park, but when I used it "Crime & Safety" was one of the top-level categories under which you could post, along with General, For Sale, etc. When you chose Crime & Safety, the maximum scope to which you could post was broadened to include your whole "wider area" which for me was all of central and north Oakland, Piedmont, and Alameda.