FORWARD CARGO DOOR OPENED AFTER TKOF. CARGO DOOR INDICATING SYSTEM WAS DEFERRED.

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FORWARD CARGO DOOR OPENED INFLT. WE RETURNED TO ZZZ FOR LNDG AND EXPECTED AND BRIEFED ILS RWY 31C CIRCLE TO LAND RWY 22L AS BROADCAST ON ATIS. THIS APCH WOULD HAVE ALLOWED TOUCHDOWN AT LESS THAN MAX LNDG WT. CHICAGO APCH THEN TURNED US TOWARD ARPT AND ASKED US TO RPT FIELD IN SIGHT FOR A VISUAL APCH TO RWY 22L. THIS SAVED ABOUT 8 MINS OF FLYING TIME AND RESULTED IN A LNDG WT POSSIBLY 500 LBS OVER MAX LNDG WT LIMIT. WE REPORTED POSSIBLE OVERWT LNDG TO MAINT AND THEY CONCLUDED NO INSPECTION WAS REQUIRED BASED ON WT AND RATE OF DSCNT AT TOUCHDOWN. WE WERE NOT AWARE FORWARD CARGO DOOR WAS OPEN WHILE INFLT AND ELECTED TO RETURN DUE TO PRESSURIZATION PROB AND UNUSUAL NOISE. FORWARD CARGO COMPARTMENT DOOR INDICATION SYS WAS DEFERRED PER MEL. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE ACFT INVOLVED WAS A CRJ700. REPORTER STATED THAT THE INOP INDICATOR REQUIRED A VISUAL INSPECTION FOR SECURITY PRIOR TO FLT. THIS WAS ACCOMPLISHED BY THE REPORTER AND GND PERSONNEL. AFTER THE ACFT RETURNED; THE DOOR WAS DISCOVERED TO BE FULLY OPEN. THE LATCHES WERE INSPECTED; AND THEY APPEARED TO BE OUT OF RIG.