THE CRAB NEBULA ONE OF THE MOST IMPORTANT AND BEST STUDIED ASTRONOMICAL OBJECTS OFTEN CONSIDERED TO BE A "STANDARD CANDLE" REFERENCE SOURCE IS NOW KNOWN TO BE VARIABLE WITH FLARES ABOVE 100 MEV ON 1-DAY TIMESCALES AND VARIABILITY UP TO ~10% ON TIMESCALES OF ~1 YEAR BELOW 100 KEV. THESE RESULTS MOTIVATE A SEARCH FOR VARIABILITY IN HISTORICAL OBSERVATIONS AND HAVE CHANGED THE WIDELY HELD VIEW THAT THE CRAB NEBULA IS A STABLE SOURCE SUITABLE FOR CALIBRATION. WE PROPOSE TO INVESTIGATE THE PAST VARIABILITY OF THE CRAB NEBULA BY REANALYZING COMPTON GAMMA-RAY OBSERVATORY (CGRO) DATA FROM THE BURST AND TRANSIENT SOURCE EXPERIMENT(BATSE 20 KEV-1 MEV) THE ORIENTED SCINTILLATING SPECTROMETER EXPERIMENT (OSSE 40 KEV-10 MEV) THE IMAGING COMPTONTELESCOPE (COMPTEL 1-30 MEV) AND THE ENERGETIC GAMMA RAY EXPERIMENT TELESCOPE (EGRET 20 MEV-30 GEV). WE WILL SEARCHFOR EVIDENCE OF FLARES IN DAILY EGRET DATA MORE THAN DOUBLING THE BASELINE FOR FLARE DETECTION LOOK FOR LOWER-ENERGY COUNTERPARTS TO FLARES AND STUDY THEIR ENERGY DEPENDENCE USING COMPTEL OSSE AND BATSE. USING THE THE CRAB PULSAR SPECTRUM FROM CONTEMPORANEOUS DATA WE WILL CROSS-CALIBRATE THE ROSSI X-RAY TIMING EXPLORER (RXTE) AND CGRO TO EXTEND OUR BASELINE FOR STUDIES OF LONG-TERM (YEARLY) VARIATIONS FROM 15 TO 25 YEARS OF NEAR-CONTINUOUS MONITORING. DATA FROM BATSE OSSE COMPTEL AND EGRET WILL BE USED TO INVESTIGATE THE ENERGY DEPENDENCE OF THESE LONG-TERM VARIATIONS WHICH HAVE NOT YET BEEN EXPLORED WITHSUFFICIENT SENSITIVITY ABOVE ABOUT 100 KEV. RESULTS FROM THIS STUDY WILL BE COMBINED WITH MORE RECENT RESULTS FROM RXTE SWIFT INTEGRAL AND FERMI TO REVEAL THE 25-YEAR BEHAVIOR OF THE CRAB. A THEORIST ON OUR TEAM WILL USE OUR RESULTS FOR THE ENERGY AND TIME DEPENDENCE OF THE FLARING AND LONG-TERM BEHAVIORS TO CONSTRAIN MODELS OF THE CRAB NEBULA AND OTHER PULSAR WIND NEBULAE.