A Maintenance and Long-Term Extension Study of the Efficacy and Safety of Upadacitinib (ABT-494) in Participants With Crohn's Disease Who Completed the Studies M14-431 or M14-433

For Substudy 1: * Participant who achieve clinical response in Study M14-431 or Study M14-433. * Participant completes study procedures in the parent study. The final endoscopy for Studies M14-431 or M14-433 may be missing, if the endoscopy cannot be performed during the COVID-19 pandemic. For Substudy 2: * Participant completes Substudy 1. The Week 52 endoscopy may be missing, if the endoscopy cannot be performed during the COVID-19 pandemic. * Participant who achieved clinical response at the time described in the protocol and completes study procedures in the parent study/ substudy.

For Substudies 1 and 2: * Participant is considered by the investigator, for any reason, to be an unsuitable candidate for the study. * Participant who has a known hypersensitivity to upadacitinib or its excipients, or had an adverse event during Studies M14-431 and M14-433 or Substudy 1 or 2 of Study M14-430 that in the investigator's judgment makes the participant unsuitable for this study. * Participant at the final visit of M14-431 or M14-433 with any active or chronic recurring infections based on the investigator's assessment that makes the participant an unsuitable candidate for the study. Participants with serious infections undergoing treatment may be enrolled BUT NOT dosed until the infection treatment has been completed and the infection is resolved, based on the investigator's assessment. * Participants with high grade colonic dysplasia or malignancy diagnosed at the endoscopy performed at the final visit of Studies M14-431, M14-433 or Substudy 1 of Study M14-430 (Week 52).