On April 8, 2004, at 1441 eastern daylight time, a Cessna 140, N527ST, registered to and operated by a private pilot, main landing gear collapsed during landing on runway 19 at Greenville Downtown Airport, Greenville, South Carolina. The personal flight operated under the provisions of Title 14 CFR Part 91. Visual meteorological conditions prevailed at the time and no flight plan was filed. The airplane was substantially damaged and the private pilot received no injuries. The flight departed Oconee County Regional Airport, Clemson, South Carolina, on April 8, 2004 at 1315. During the personal flight, the pilot made initial contact with the Greenville Downtown Airport tower six miles from the airport and was given instructions to enter the right downwind for runway 19. The pilot was cleared to land and went through his approach checklist with everything normal. The airplane crossed over the landing threshold and settled onto the runway in a three point landing attitude. During landing roll, the pilot felt the left wing start to dip and the airplane vibrating. The airplane turned approximately 20-degrees to the right, the left front side struck the runway and the airplane came to a stop. The pilot had completed a series of touch and go landings, and during the accident landing, the leaf spring gear assembly broke. The fracture faces were removed and preserved for further examination. Further examination revealed that the leaf spring gear strut fracture stemmed from an area of fatigue cracking that initiated at the upper forward side of the inboard hole for the step attachment bolts. Given the observed corrosion in the bolt hole, it was determined that the fatigue originated from corrosion pitting. For fatigue to initiate at the upper side of the spring strut, the upper side must have been placed in tension. According the the aircraft maintenance logbook for the 1946 built airplane, the leaf spring gear assembly and the total airframe time was 3,375 hours.