Boeing kehitti P-12:sta omalla kustannuksellaan Model 89:na. Se lensi ensilentonsa Yhdysvaltain laivaston koekeskuksessa Anacostiassa, Marylandissa 7. elokuu 1928. Boeing käytti XP-9-koemallista saamiaan kokemuksia kehittäessään puolikantavalla kokometallirungolla varustetun P-12:sta (Boeing Model 218).
Model 218 testattiin XP-925-mallinimellä ja kehittelyn tuloksena USAAC tilasi sitä 135 kappaletta P-12-E ja -F malleina
The Boeing P-12/F4B was an American pursuit aircraft that was operated by the United States Army Air Corps and United States Navy.
Length: 20 ft 4 in (6.19 m)
Wingspan: 30 ft (9.14 m)
Height: 9 ft (2.74 m)
Loaded weight: 2,690 lb (1,220 kg)
Powerplant: 1 × Pratt & Whitney R-1340-17 Radial engine, 500 hp (373 kW)
Maximum speed: 189 mph (304 km/h)
Cruise speed: 160 mph (257 km/h)
Range: 570 miles (917 km)
Service ceiling: 8,020 m (26,300 ft)
Armament: Two 7.62 mm mg or one .30 inch (7.62 mm) and one 12.7 mm mg
Bombs: 244 lb (111 kg) of bombs carried externally.
This resulted in a higher top speed and overall better performance. As result of Navy evaluation 27 were ordered as the F4B-1, later evaluation by the United States Army Air Corps resulted in orders with the designation P-12. Boeing supplied the USAAC with 366 P-12s between 1929 and 1932. Production of all variants totalled 586.
P-12s were flown by the 17th Pursuit Group (34th, 73rd, and 95th Pursuit Squadrons) at March Field, California, and the 20th Pursuit Group (55th, 77th and 79th Pursuit Squadrons) at Barksdale Field, Louisiana. Older P-12s were used by groups overseas: the 4th Composite Group (3rd Pursuit Squadron) in the Philippines, the 16th Pursuit Group (24th, 29th, 74th, and 79th Pursuit Squadrons) in the Canal Zone, and the 18th Pursuit Group (6th and 19th Pursuit Squadrons) in Hawaii.
The P-12 remained in service with first-line pursuit groups until replaced by Boeing P-26s in 1934–1935. Survivors were relegated to training duties until 1941, when most were grounded and assigned to mechanic's schools.