On September 5, 1999, at 1100 central daylight time, a Cessna 190, N9872A, left main landing gear collapsed during a normal landing at the Enterprise Municipal Airport in Enterprise, Alabama. The personal flight was operated by the pilot under the provisions of Title 14 CFR Part 91 with no flight plan filed. Visual weather conditions prevailed at the time of the accident. The airplane sustained substantial damage. The commercial pilot and pilot/passenger were not injured. The flight departed Enterprise, Alabama, at 1000. According to the pilot, after approximately one hour of pleasure flying in the local flying area, the two pilots returned to Enterprise. After touchdown, the airplane had rolled several hundred feet, when the pilot felt an unusual sensation in the airframe. At approximately the same time, the left spring leaf landing gear assembly separated from the airframe, and the airplane fell to the ground. The field examination of the fracture face disclosed evidence of a preexisting fracture in the steel material. During the follow-up examination of the fracture face, with the aid of a bench binocular microscope, revealed the presence of at least three small fracture areas typical of fatigue cracking. The width of the fatigue fracture on the surface of the spring was about 0.15 inches. The depth of the fatigue cracking extended to a depth of approximately 0.06 inches. The origin of the fatigue cracking was damaged during the ultimate separation. The examination also disclosed that the fatigue origin was located in an area that showed fretting damage.