UNAUTH PENETRATION OF AIRSPACE. PROX OF ATA.

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WE WERE ON A VFR SIGHTSEEING FLT TO SEE THE FLOODED CONDITIONS OF THE MISSOURI & MISSISSIPPI RIVERS. LCL NOTAM REQUIRED ALL VFR TFC TO OBTAIN ADVISORIES IF SIGHTSEEING OVER THE RIVER IN THE VICINITY OF ST. LOUIS TCA. AS A RESULT; THE FREQ WAS VERY CROWDED WITH A LARGE NUMBER OF ACFT. EVERYONE WAS MAKING STRANGE CIRCLING REQUESTS TO PHOTOGRAPH OR OTHERWISE LOOK AT OBJECTS ON THE GND. AS WE FLEW AROUND THE NE SIDE OF THE TCA; WE WERE GIVEN 'TFC; 10 O'CLOCK; SLOW MOVING; LESS THAN A MI; TYPE AND ALT UNKNOWN' BY ST. LOUIS APCH. WE WERE 9 NM N OF DOWNTOWN (CPS) ARPT AND INDICATING 210 KTS IN A DSCNT. I DIDN'T WANT TO LEAVE APCH UNTIL THE TFC WAS SIGHTED. AT THIS POINT; WE SAW THE TFC; A HELI; LOW AND TO THE L. HE WAS NO FACTOR. UNFORTUNATELY; LOOKING FOR THE TFC HAD BEEN A DISTR. I FAILED TO PLAN AHEAD FOR MY ENTRY OF CPS'S ATA. SEEING US NOW ONLY 5.5 NM FROM THE ARPT; I RUSHED TO GET THE TWR FREQ FROM AN ELECTRONIC MOVING MAP. I HAD THE WRONG ARPT SELECTED! WITHOUT DOUBLE-CHKING THE IDENT OF THE ARPT; I CALLED UP THE INFO PAGE; SAW THE 'TWR FREQ' AND ENTERED THAT FREQ INTO THE COM. I RPTED '4 MI N; REQUESTING LOW PASS' (WE HAVE A HANGAR AT THAT ARPT (CPS) AND WANTED TO SEE HOW CLOSE THE FLOOD WATER HAD GOTTEN). THE TWR RESPONDED 'CLRED FOR LOW APCH; RPT 2 MI FINAL FOR RWY 17.' ALTHOUGH I FLY REGULARLY FROM CPS; I FAILED TO RECOGNIZE THAT: 1) THE TWR FREQ WAS FOR ALN; APPROX 15 MI BEHIND ME; NOT DOWNTOWN; IMMEDIATELY AHEAD. 2) ALN HAS RWY 17; DOWNTOWN RWY 22. I RPTED '2 NM FINAL FOR THE LOW PASS.' ALN SAID 'NOT IN SIGHT; CLRED FOR LOW PASS; RWY 17.' IT WAS THEN THAT I REALIZED I WAS BLASTING THROUGH CPS'S ATA AT 300 FT AGL WHILE TALKING TO A DIFFERENT TWR. I CALLED THE TWR AFTER LNDG. NEITHER THEY NOR ANY OTHER TFC WERE AWARE OF MY LOW PASS. IN 20 YRS OF FLYING I'VE NEVER HAD A SIMILAR MISCOM WITH THE WRONG TWR. DISTR GOT THE BETTER OF ME.