Mr. Ashenfelter, a slender, 128-pound special agent in the FBI's Newark field office, arrived at the Summer Games in Helsinki as something of an afterthought. The United States was squarely focused on outshining its geopolitical rival, the Soviet Union, which claimed to have been training a group of 20,000 "drafted" athletes and was competing in the Games for the first time since the country's formation in 1922.
But while the Games were in some ways a throwback to the 1936 Olympics in Berlin — a battle of propaganda as much as athletics, when African American track star Jesse Owens won four gold medals in a stadium filled with Nazi imagery and boasts of Aryan superiority — Mr. Ashenfelter's appearance was hardly expected to provide a patriotic boost, let alone a medal-winning podium appearance.
Few Americans were familiar with his event, an equestrian-inspired, 3,000-meter footrace in which athletes must clear 28 barriers and seven water pits, shallow pools that follow three-foot-high barriers. The sportswriter Red Smith once quipped that it was the kind of race that would make "splendid training for a man who expects to get trapped in a pasture with an enraged bull."
In Helsinki, the event was assumed to be an easy gold-medal victory for the Soviets, who were represented by record-setting athlete Vladimir Kazantsev. No American had won an Olympic steeplechase event since James Lightbody took the gold in 1904, and Mr. Ashenfelter said he had competed in the steeplechase just eight times previously.
Still, his wife, Lillian, recalled in a phone interview, "The night before the race he said simply, 'I'm going to win tomorrow.' "
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Mr. Ashenfelter, the confident son of New Jersey apple farmers, had initially sought to become a baseball player while studying at Pennsylvania State University. He took up running after a friend told him it was an easy ticket to a free locker, towel and hot shower on campus, his wife said, and soon won a slew of cross-country races, both in college and as an amateur representing the New York Athletic Club.
Preparing for the Olympics in and out of the office, he worked overtime at the FBI, accruing the vacation hours his bosses required for a trip abroad, while training an hour or so each day. Racing up the stairways at work, he also worked out at a local park after putting his children to bed each night. Park benches, and what his wife remembered as a wooden horse he hid in the bushes, functioned as faux steeplechase barriers on his runs.
Preparing for the course's water pits proved more of a challenge. The sloping pools stretch about 12 feet from the barriers, which runners leap off in an effort to propel themselves to the shallows, where the water is only a few inches deep. Mr. Ashenfelter's form was reportedly a work in progress even at the time of the Games, when according to a syndicated column by Smith, he altered his landing at the suggestion of a few Scandinavian competitors, hitting the water with one foot instead of two.
The adjustment proved crucial. Before a crowd of about 70,000 people, Mr. Ashenfelter made the run of his life in the Olympic finals, going elbow-to-elbow with Kazantsev for much of the race. His last of seven laps, clocked in at 1 minute and 8.6 seconds, "would be an excellent sprint for a distance man running on the flat," the Associated Press wrote at the time. "For a man in the steeplechase, it was of heroic proportions."
Jumping off a barrier and into the final water pit, Mr. Ashenfelter landed in stride and, amid the roar of a crowd that sensed the possibility of one of the Games' great upsets, launched into an unexpected sprint. His rival stumbled out of the water, appearing to lose energy, and Mr. Ashenfelter won not by a hair but by about 30 yards — a margin of some six seconds, an eternity in an Olympic race.
Although steeplechase records were not officially tracked for another two years, Mr. Ashenfelter's time of 8:45.4 was considered a world record. Mr. Ashenfelter, sometimes known by the childhood nickname of Nip, became a national sensation. FBI chief J. Edgar Hoover sent his "heartiest congratulations" in a cablegram, and later that year Mr. Ashenfelter received the American Athletic Union's prestigious James E. Sullivan Award, given to the nation's most outstanding amateur athlete.
Mr. Ashenfelter was the last American to receive gold in the steeplechase, and his medal served as one of 76 that helped the United States edge the Soviet Union's count of 71. But his celebrity status seemed driven as much by his medal as by his mystery-shrouded occupation.
As some newspapers jokingly put it, according to a history of the Olympics by sportswriter David Goldblatt, Mr. Ashenfelter was distinguished in large part as "the first American spy who had allowed himself to be chased by a Communist."
Horace Ashenfelter III was born in Phoenixville, Pa., a suburb of Philadelphia, on Jan. 23, 1923. He was raised in nearby Collegeville and played football, basketball and baseball in high school before attending Penn State.
His studies were interrupted by World War II, when he served three years in the Army Air Forces as an aerial gunnery instructor, flying armored planes that other pilots attempted to shoot with frangible bullets that were designed not to puncture the aircraft.
Mr. Ashenfelter graduated in 1949 with a bachelor's degree in physical education, and — while beginning his career at the FBI — remained at the school to receive a master's degree in education in 1955. Contrary to public speculation, he said his FBI career was fairly uneventful; for the most part, his years were spent checking federal job applicants for communist affiliations.
Anticipating a new assignment at the bureau that would force his family to move out of the Newark area, he left the FBI in 1959 to work as a salesman in the precious-metals industry. He later started his own metal refining company and retired in 1993.
Survivors include his wife of 73 years, the former Lillian Wright of Glen Ridge, N.J.; four sons, Horace Ashenfelter IV of Rochester Hills, Mich., James Ashenfelter of Glen Ridge, Thompson Ashenfelter of Needham, Mass., and John Ashenfelter of Chatham, N.J.; a brother; a sister; 12 grandchildren; and four great-grandchildren. A younger brother, Bill Ashenfelter, died in 2010; all three brothers ran on a four-mile relay team at Penn State, and Bill competed alongside Mr. Ashenfelter at the 1952 Games before setting a world record in the two-mile relay.
Mr. Ashenfelter was inducted into the National Track & Field Hall of Fame in 1975 and won 17 national running championships, according to the hall, before retiring after the 1956 Olympics in Melbourne, Australia.
He was simply too old, he said after leaving the Games without making the steeplechase finals. His qualifying time, however, would have been good enough for the silver medal four years earlier.