National:
Reference USA - 40 million businesses
also, 2 modules: New Businesses - about 4 million companies ; Historical Businesses
Mergent Intellect - more than 70 million US companies, plus more than 200 million global companies. Replaces D&B Million Dollar Database
PrivCo - 400,000 private companies in the US - has many M&A and private equity deals. Note: create individual account.
ThomasNet (formerly, Thomas Register)
Brands and Their Companies - via Gale Directory Library database
Ward's Business Directory of U.S. Private and Public Companies - 100,000 companies - via Gale Directory Library database
LexisNexis Directory of Corporate Affiliations (within Nexis Uni). From "Menu", select "Company Dossier"
Print editions of older directories -- offsite, Library Services Center
LexisNexis Directory of Corporate Affiliations - from 1967 to 2016 - offsite, Library Services Center - HG4057.A219 [note: slight title changes during these years]
Pratt's Guide to Private Equity Sources - offsite, Library Services Center - REFERENCE HG64.P73 -- 2003 to 2015 [previous title, Pratt's Guide to Venture Capital Sources -- REFERENCE HG65.G83 -- 1996-2002]
Standard & Poor's Register of Corporations, Directors, and Executives - offsite, Library Services Center - REFERENCE HG4057.A4 - 1963-2011 [slight title change] (Geographical Index volumes are call number: REFERENCE HG4057.A41)
Thomas Register (on microfilm, 1905-2006) - offsite, Library Services Center - TS199.T45
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Brands and Their Companies - offsite, Library Services Center - T223.V4 A2225x - from 1990 to 2011
Companies and Their Brands - offsite, Library Services Center - REFERENCE T223.V4 A253 - 1990 to 2011
Corporate Yellow Book - 2016 ed. only -- offsite, Library Services Center - REFERENCE HG4057.A15646
D&B Business Rankings - offsite, Library Services Center - REFERENCE HG4057.A237 - 1982 to 2017
D&B Consultants Directory - offsite, Library Services Center - REFERENCE HD69.C6 D86x - 1986 to 2017 [2017 is "Core Reference"]
D&B Industrial Guide - offsite, Library Services Center - REFERENCE TS203.D8 - 2015-2017 [2017 is "Core Reference"]