Cook Associates (Cook) (plaintiff), an Illinois employment agency, entered into a contract with Lexington United Corp. (Lexington) (defendant), a Delaware corporation whose principal place of business is St. Louis, Missouri. The contract required Lexington to pay Cook a fee if Lexington filled its sales management position with an applicant referred to Lexington by Cook. Joseph Runza, an executive at Lexington, met with Gregg Hoegemeir, one of the prospective employees whose name and resume was sent to Lexington by Edith McIntosh, a Cook employee, in Chicago and offered Hoegemeir the field sales manager position. Hoegemeir rejected the offer. Subsequently, McIntosh’s employment with Cook terminated, and she opened her own employment agency. Soon thereafter, Runza asked for McIntosh’s help in finding a sales manager for Lexington. McIntosh provided Hoegemeir’s information. Runza offered Hoegemeir the national sales manager position and Hoegemeir accepted. Cook demanded its fee. Lexington refused to pay the commission, and Cook sued Lexington for breach of contract in an Illinois state court. Lexington moved to set aside the service of process upon its president at a trade show in Chicago on the grounds that the trial court lacked personal jurisdiction because the action did not arise from the transaction of any business by Lexington in Illinois, as required by Illinois’ long-arm statute. The trial court denied Lexington’s motion and entered judgment in favor of Cook. The court of appeals reversed, holding that the trial court lacked personal jurisdiction over Lexington. Cook appealed on the grounds that the Illinois long-arm statute granted the trial court’s personal jurisdiction over Lexington because Lexington had done business in Illinois, and under the due process standard of minimum contacts.