Business directories: The NJ State Library seems to offer some resources about NJ businesses. A visit to that library (and conversation with librarians there) might be necessary
Local news media:
The Library of Congress's Chronicling America is a treasure trove of historical newspapers. On the site's home page, try limiting by publication year, state, and topic.
Black Freedom Struggle in the 20th Century is a database focused on the political side of the freedom movement, the role of civil rights organizations in pushing for civil rights legislation, and the interaction between African Americans and the federal government in the 20th Century (covering the time period 1901-1991).
Genealogy tools [Our options are limited on this front, but I'll keep exploring]
"Trenton Illustrated by Ellwood Parsons Robbins was published by H.R. Page & Co. in 1891. It includes historic photographs of Trenton, including buildings, streets, parks and scenic views." (NJ State Library)