What was found
AFTER TAKEOFF, THE FLIGHT CREW PERFORMED A LANDING GEAR UPLATCH CHECK. THE LEFT MAIN LANDING GEAR UNSAFE LIGHT REMAINED ILLUMINATED. LANDING GEAR WAS RECYCLED WITH A NOSE LANDING GEAR UNSAFE LIGHT ILLUMINATION UPON LANDING GEAR RETRACTION. FLIGHT RETURNED TO MSP AND LANDED WITHOUT INCIDENT. LANDING GEAR INDICATION WAS NORMAL UPON LANDING. MAINTENANCE PERFORMED A LANDING GEAR UPLATCH CHECK AND REPLACED THE LANDING GEAR CONTROL UNIT. OPERATIONAL CHECK NORMAL.