Start with him Data Axle Reference Solutions (formerly ReferenceUSA) to find prospects and competitors by industry and location. Includes a directory of over 15 million U.S. public and private companies. (Rutgers-restricted access)
MarketLine is useful for public company profiles, SWOT analyses, financial deals, and market share. (Rutgers-restricted access)
PrivCo is an excellent resource for business and financial research on non-publicly traded companies, including family-owned, private equity-owned, venture-backed, and international unlisted companies. The database currently includes profiles for over 900,000 companies, 20,000 private equity and venture capital firms and investors, and 100,000 private market deals. (Rutgers-restricted Access)
Westlaw includes Hoover's reports on companies and their competitors. (Rutgers-restricted access)
A quick overview of the business environment in your city, county or state can be found at QuickFacts from the US Census Bureau. How to search video
Current numbers for both the County Business Patterns and the Nonemployer Statistics are now part of the https://data.census.gov website. How-To Video (Silent)
Past data for the number of establishments with employees in each industry, broken down by employee size, may be found in County Business Patterns (organized by NAICS).
Past data for businesses without employees run by the self-employed are located at the Nonemployer Statistics for states, metro areas, and counties (also organized by NAICS).