The Kansas City AC Blue Diamonds, of Kansas City, Missouri, was the premier power in AAU basketball during the early 1920s. The Blue Diamonds from 1920 to 1931 placed in the two three nine times, taking two AAU national tournament titles, five second place finishes, and two third place finishes. From 1920 to 1926, Kansas City AC never took less than third place.

The history of the Kansas City Athletic Club can be traced back to 1887, when Arthur E. Stillwell developed Fairmount Park between Kansas City and Independence, he included athletic facilities on the site. To encourage their use, the Fairmount Cycling Club was formed. The club flourished and in 1893 changed its name and structure to become the Kansas City Athletic Club, a $50,000 stock corporation. A rise in membership and stature took place in the first years of the twentieth century as KCAC athletic teams, especially basketball teams, drew national attention in various tournaments.

The Kansas City Athletic Club emerged as a basketball power in 1905 when it beat the legendary Buffalo Germans, who were considered the national champions based on their 1904 Olympics championship. A player on the KC team was the legendary Phog Allen. In the 1905-06 season the team garnered a 13-4 record, beating such teams as University of Nebraska and Company E of Schenectady, New York.

The 1906-07 saw Kansas City AC garner a 14-3 record, beating such teams as Yale University, Kansas University, and Iowa Hawkeyes|Iowa University]].Following World War I, membership surged and Kansas City AC looked for a new home. A twenty-two story hotel structure at the corner of Eleventh and Baltimore in downtown Kansas City had been started but never completed. The KCAC acquired rights to the structure, completed it, and opened their new facility as a club and residential hotel in 1923. During the 1920s the club flourished, membership grew and the organization was financially sound.

The Kansas City AC basketball team was attracting notice at this time, notably in 1920, when it took third place in the AAU tournament held in Atlanta. The following year, Joseph A. Reilly, director of the Kansas City Athletic Club, offered to host the AAU tournament, which would be held in Convention Hall. His offer was accepted and for the first time since its founding in 1897 the AAU tournament had a true national character, with 32 teams from across the country converging on Kansas City.

The Blue Diamonds were a formidable host, featuring the great Forrest “Red" DeBernardi, scoring machine Milton Singer, and Arthur “Dutch” Lonberg, a future collegiate coach at Washburn College and Northwestern University. Although the teams came from far and wide, three of the four finalists were from Kansas, and Kansas City, Missouri. The team was coached by Henry Ashby. At the 1921 tournament, Kansas City beat the University of Nevada, 40-19, in the quarterfinals; Lowe & Campbell, 42-31, in the semifinals; and Southwestern College of Winfield, KS, 42-36, in the championship game. Singer and DeBernardi were chosen as tournament all-stars, called All Americans.

In the 1921-22 season, Kansas City AC still had a formidable team, and once again played host to the tournament. They Blue Diamonds smashed Union Club of Belvedere, IL, 50-28, in the quarterfinals; and blew past the Indianapolis YMCA, 58-27, in the semifinals. However, in the championship game, the Blue Diamonds were upset by Lowe & Campbell, 42-28. Lowe & Campbell was a sports store in Kansas City, and it sponsored teams had become a powerful rival to the Blue Diamonds. Again three of the four finalists were from Kansas and Missouri. DeBernardi and George Hess made the all-star team for the Blue Diamonds.

The 1922-23 season, Kansas City AC was out for blood. Although the team had lost DeBernardi to a new power, the Hillyard All Shines, from St. Joseph, Missouri, most of the players were veterans and were still helmed by Henry Ashby. They also recruited two players from Lowe & Campbell, George Williams and George Reeves. The quarterfinals saw the Blue Diamonds defeat the Kansas City Tabernacles, 35-15; and the semifinals saw the team prevail over Two Harbors All Stars, from Two Harbors, MN, 42-24. The championship game saw the Blue Diamonds achieve their redemption and obtain their second title, beating the Hillyard All Shines, 31-18, in an all-Missouri final. The first-string all-star team were all Kansas City AC players—George Reeves, Milton Singer, George Williams, Robert Sanders, and George “Pidge” Browning.

The 1923-24 season was another bright season for Kansas City AC. In the AAU tournament, it crushed Washburn College of Topeka, KS, 58-25, in the quarterfinals; and destroyed Lombard College, of Galesburg, IL, 38-21, in the semifinals. The championship game was a different matter, however, as the Blue Diamonds succumbed to a superbly coached Butler University team under Pat Page, 30-26. The Blue Diamonds placed three players on the tournament all-star team—three Georges, Reeves, Browning, and Williams.

In the 1924-25 season, the still formidable Kansas City AC Blue Diamonds were one of the favorites to win the annual AAU extravaganza. In the quarterfinals, they beat Lombard College, 34-26; but in the semifinals had to meet new power Hillyard Shine Alls, and lost 19-14. The Blue Diamonds found a bit of redemption, beating the Monon Athletic Club of Lafayette, IN, 29-16. Only one Blue Diamond was selected as an All American, Tusten Ackerman.

Kansas City AC was ready for a big comeback in the 1925-26 season, and at the AAU tournament destroyed Werner-Werner, of St. Louis, 44-28, in the quarterfinals; and routed a soon to be legendary amateur power, Akron Goodyear Wingfoots, 33-16, in the semifinals. Alas, in the championship game, Kansas City AC ended up in second place for the third time, losing to their biggest nemesis, the Hillyard All Shines, 25-20. Two Blue Diamonds made the all-star team, Ackerman and Verne Wilkens.From 1920 through 1926, Kansas City AC was always among the top three finalists of the AAU tournament, but that string ended in 1926.

Kansas City AC failed to make it to the quarterfinals in the 1927 tournament. The team had worked to improve the team by recruiting a bunch of University of Kansas stars. But the team was upset in tournament play by a ball-control team, the Ke-Nash-A, from Kenosha, WI, and failed to make it to the quarterfinals. The Blue Diamonds bounced back in 1928, bringing back some of the feeling of the earlier glory years. The AAU tournament saw the Blue Diamonds defeat Rockhurst College, of Kansas City, MO, 36-23, in the quarterfinals; and destroy Sterling Milk of Oklahoma City, 28-15, in the semifinals. But in the championship game, it was second place fourth time, as the team lost a heartbreaker to a new power, Cook’s Paint Boys of Kansas City, MO, 25-23, in an all-Kansas City, Missouri, final. Two Blue Diamond players, Ed Hogue and Frank “Buck” Weaver,” were selected as All Americans.

In the 1929 tournament Kansas City AC once again failed to reach the quarterfinals. In the 1929-30 season, Kansas City AC did not field a team during the regular season, but in the 1930 tournament, it did manage to reach the quarterfinals, but lost the game to the San Francisco Olympic Club, 30-25. The 1931 tournament was Kansas City AC last hurrah in the AAU tournament, but it was a surprisingly successful one. The team beat old Kansas City rivals, Lowe & Campbell, 25-21, in the quarterfinals; and Young Men’s Institute, of San Francisco, 23-17, in the semifinals. In the championship game, Kansas City AC took its fifth second place trophy, losing to a new power, Henry Clothiers of Wichita, Kansas, 38-14. Blue Diamonds Paul Burks and Frank “Buck” Weaver were named to the all-star team.

Kansas City AC was one of the last of the powerful amateur club teams to made an impact in the AAU tournament. Its success was partially helped by the AAU tournament being hosted in Kansas City during its heyday and having large partisan fans rooting the Blue Diamonds on. Thereafter, the tournament was dominated by industrial teams.