Diegel, Leo H. (27 Apr. 1899-8 May 1951), professional golfer, was born in Detroit, Michigan, the son of William G. Diegel, an industrial worker, and Elizabeth Kebbe. As a ten-year-old parochial school student he began caddying and became something of a teenage phenomenon. At age thirteen he won the city caddy championship, and four years later, as an assistant professional at the Country Club of Detroit, he won the Michigan Open title. He rose to national prominence in 1920 when he tied for second place, behind Englishman Ted Ray, in the U.S. Open at Inverness Country Club in Toledo, Ohio. This event proved to be a turning point in American golf. It marked the end of British dominance in major tournaments and the emergence of American professionals such as Diegel, Walter Hagen, Gene Sarazen, and the transplanted "Silver Scot," Tommy Armour, as well as amateur Bobby Jones. It was also the first national championship in which professionals, heretofore considered socially inferior employees, were extended full clubhouse privileges. The Open at Inverness also began a period that spawned the modern tournament circuit, or "tour," of the Professional Golfers Association (PGA), founded in 1916.

From his first official victory in 1920 to his thirty-first and last in 1934, Diegel was a tour pioneer. Having won one tournament each year from 1920 through 1923, he entered the prime of his career in 1924. That year he earned his first significant victory, the Canadian Open; he would also win this event in 1925, 1928, and 1929. Five titles in 1925 earned him the number one position that year among the top 25 competitors. He won four tournaments each in 1928 and 1929, including consecutive PGA championships, and in so doing he broke Hagen's string of four straight triumphs. Three victories in 1930 concluded this exceptional span. Thereafter, he won once in 1933 and twice in 1934. Because of his superb record he played on four Ryder Cup teams (1927, 1929, 1931, 1933) in the biennial matches against British professionals. For the period 1916 to 1929, he ranks third (behind Hagen and Johnny Farrell) in PGA winnings.

During a time when golf professionals rarely earned a living strictly from playing in tournaments, Diegel parlayed his growing reputation and engaging personality into a succession of prestigious club positions. In 1921 he became head professional at Lochmoor Country Club in Detroit. The next year he moved to the New Orleans Country Club, and in 1925 he became affiliated with the Fenimore Country Club in White Plains, New York. From 1929 to 1933 he was associated with the new Agua Caliente course in Tijuana, Mexico, as winter professional for the then princely salary of $15,000. During the late 1920s he was also a private teaching professional; his clients included motion picture mogul Adolph Zukor, film producer Joseph Schenck, and actor Douglas Fairbanks. The Hollywood connection resulted in Diegel and his friend Hagen costarring in a Mack Sennett golf comedy. In 1934, during the second of his 12 years with the Philmont Country Club in Philadelphia, he married Violet Bird. The couple was childless.

After 1934 Diegel's tournament presence and performance abruptly declined. He injured his right shoulder in 1935 while roughhousing with fellow tour player Harry Cooper and was forced to forgo much of the 1936 season. A second injury in 1938 to his right hand and thumb, the result of being struck by an automobile while crossing a street, was a further setback. His last noteworthy, top-25 finish in a PGA event occurred in 1939. During World War II he chaired the PGA Rehabilitation Committee, actively promoted golf in the convalescence of wounded service personnel, and raised some $600,000 for the construction of golf facilities at veterans' hospitals. In 1945 he became the professional at the El Rio Country Club in Tucson, Arizona; returned to the Detroit Country Club in 1949; and in 1950 relocated in southern California. A heavy smoker, Diegel was diagnosed in 1947 with throat and lung cancer, the cause of his death in North Hollywood, California. In 1955 he was posthumously elected to the PGA Hall of Fame.

Because he came close but never won either the U.S. Open or the British Open, Diegel is remembered as a near-great player who fell short of expectations. Writers have attributed this predicament to his temperament, variously described as high-strung, jittery, and fidgety; the golf historian Al Berkow referred to it as something akin to "exposed ganglion." His frenetic tournament behavior included sticking the lighted end of a cigarette in his mouth and ramming a two-foot putt into a sand trap. He was especially vulnerable to psychological manipulation during match, or head to head, play involving the irrepressible Hagen, his competitive nemesis but close personal friend. To combat his tendency to jerk critical short putts to the left, in 1924 he adopted a unique style in which he bent over from the waist, aligned his arms almost horizontally over the target line, and locked his hands so as to eliminate all wrist movement from the stroke. While "Diegeling," as it was called, was effective in lesser tournaments, it never produced the foremost national championships. This limitation was especially apparent in the U.S. Open; he told an interviewer in 1929 that he could never seem to develop "the proper frame of mind" for the event (Price, American Golfer, p. 122). Fellow professionals held his wood and iron play in high regard, and when his "arms-akimbo" or "flying elbows" putting technique was working "the Dieg" was considered unbeatable. Bernard Darwin, the London Times golf writer, referred to him as "in a way the greatest golfing genius I have ever seen" (Wind, American Golf, p. 254). His grasp of the game matched his execution, as revealed in his respected instructional book, written with Jim Dante, The Nine Bad Shots of Golf and What to Do about Them (1947), which justified seven printings. His notion of an arms-and-hands putting stroke anticipated a more mechanical approach in the latter half of the twentieth century. Ironically, a few missed putts denied him the greatness equated with "major" tournament victories.

During Diegel's prime in the late 1920s, W. D. Richardson, golf writer for the New York Times, contributed "Diegel the Dazzling" to the American Golfer magazine; it was reprinted in Charles Price, The American Golfer (1964), a collection of articles from that magazine. Herbert Warren Wind analyzes Diegel's brilliance and his failures in The Story of American Golf: Its Champions and Its Championships (1948; repr. 1986) and to a lesser extent in Following Through (1985). Robert Sommers, The U.S. Open: Golf's Ultimate Challenge (1987; 2d ed., 1996), is insightful regarding the elusive American championship. Al Barkow, Golf's Golden Grind: The History of the Tour (1974) and The History of the PGA Tour (1989), cover Diegel's role as a tour pioneer; the latter title, when used with John P. May, ed., The Golf Digest Almanac, 1984 (1984), presents his career statistically. Additional insights are in Bernard Darwin, Golf between Two Wars (1944; repr. 1985); the editors of Golf Digest, All about Putting (1973); Will Grimsley, Golf: Its History, People & Events (1966); Walter Hagen, The Walter Hagen Story (1956); George Peper, ed., Golf in America: The First One Hundred Years (1988); and Charles Price, The World of Golf: A Panorama of Six Centuries of the Game's History (1962). Obituaries are in the Detroit News and the Los Angeles Times, 9 May 1951.