12.1 Is the company a parent or a subsidiary company?
12.2 Is the parent U.S. or foreign-owned?
Most, but not all, publicly traded firms are parent companies. One of the difficulties researchers encounter when they want to gather information at a divisional or subsidiary level is that all SEC filings are for the parent company. If your target firm does have a parent company, you will find that information in Form 10-K or the DEF14A (Proxy statement) available from the SEC EDGAR database. Parent companies may own a significant amount of stock and/or have representatives on the Board of Directors.
CrocTail also provides links from parent companies to subsidiaries, and from subsidiaries to the ultimate parent.
Crunchbase is a free option for getting info on corporations, including acquisition history.
UMass Resources (for UMass students only)
Mergent Intellect allows you to link-down to subsidiaries as well as link-up to a larger parent company through their Family Tree.
ReferenceUSA and Westlaw are also comprehensive corporate business database and both provide information on corporate family trees.