On July 22, 2003, about 1400 eastern daylight time, a Boeing 757-251, N504US, operated by Northwest Airlines Inc. as flight 1142, was not damaged during an encounter with turbulence, while climbing near Wadsworth, Ohio. Two certificated airline transport pilots, one flight attendant, and 107 passengers were not injured. Two flight attendants sustained minor injuries, and one flight attendant sustained a serious injury. Visual meteorological conditions prevailed for the flight that departed Detroit Metropolitan Wayne County Airport (DTW), Detroit, Michigan; destined for Baltimore-Washington International Airport (BWI), Baltimore, Maryland. An instrument flight rules flight plan was filed for the scheduled air carrier flight conducted under 14 CFR Part 121. The captain stated that the airplane was climbing through 29,000 feet, and encountered unreported "Code 4" clear air turbulence for approximately 30 seconds. The lead flight attendant reported that a flight attendant in the rear galley had suffered a head injury, and was bleeding. Another flight attendant suffered a possible broken finger, and a third flight attendant reported a sore neck. The captain diverted the flight to Cleveland, Ohio, and landed uneventfully. The captain also noted that no passengers complained of any injury, and the seatbelt sign was illuminated. The flight attendant that suffered a head injury was admitted to a local hospital for more than 48 hours for observation.