As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFTER TAKEOFF WHEN SELECTING GEAR UP ALL 3 GEAR REMAINED EXTENDED AND "GEAR DISAGREE" MSG ILLUMINATED. FOLLOWED QRH PROCEEDURES" GEAR UP DISAGREE" GEAR DISAGREE MSG DISAPPEARED. A/C RETURNED TO ATL AFTER T/O, AN EMERGENCY WAS DECLARED.