Was the ruling on the Supreme Court case Muller v. Oregon ever overruled?

No it was never overruled. The court ruled there was no constitutional violation. The factory and laundry owners claimed that there was no reasonable connection between the law and public health, safety, or welfare. Muller v. Oregon

Thanks, Sagus. I never read that it was overruled, but I would have thought that eventually someone would try to take advantage of the ruling (made with discriminatory thought of 100 years ago which has proved to be an incorrect discrimination) and this would cause the court to overturn the ruling.