1957 - The Kansas City Athletics ship pitchers Art Ditmar, Bobby Shantz, and Jack McMahan, and infielders Clete Boyer, Curt Roberts and Wayne Belardi to the Yankees. In return they receive pitchers Mickey McDermott, Tom Morgan, Rip Coleman and Jack Urban, OF Irv Noren, plus infielders Billy Hunter and Milt Graff. Roberts didn't go to New York City till May 4, while Boyer went a month later. Hunter and Urban don't switch until April 5. The veteran Shantz and Boyer will be valuable pickups for New York, with Shantz leading the American League in ERA this year, and Boyer a tough defensive 3B for eight years in pinstripes. The A's will eventually admit that when they signed Boyer for a $40,000 bonus in 1955, it was on behalf of the Yankees, with the understanding that they'd later ship him to NY.
A now-dated Baseball Almanac essay took a look at the KC-NYY underground "shuttle" with a particular focus on the 1955-60 seasons, though it was in effect for a good part of the 1950's and 60's. From the accompanying essay:
Of course, the Yankees were the richest and most resourceful club in baseball, then as now, and they found a way to ensure a continuous supply of good players. They managed to turn one of their American League rivals, the Kansas City Athletics, into a virtual farm team.
How did this happen? Connie Mack's family sold the Philadelphia Athletics in 1954, and Yankee principal owner Dan Topping arranged for one of his business friends, Arnold Johnson, to buy the A's and move the team to Kansas City. It's still unclear how much influence the Yankee ownership held over the A's, but the two teams then embarked on a six-year series of trades. These trades, as we shall see, almost always favored the Yankees.
The Yankees, in fact, rarely traded players with any other team in this six-year period. From 1955 to 1960, the Yankees gained many outstanding players from Kansas City, and managed to give only marginal value in return. It must have worked, since the Yankees won four more pennants in a row beginning in 1955, while the new Kansas City team struggled to stay out of last place.
BONUS MATERIAL: For more reading material on this strange dynamic period, I'll point you to a few pages from The Kansas City Athletics: A Baseball History, 1954-1967 By John E. Peterson. Take a read from page 138-139.
EXTRA CREDIT READING: If you're so inclined, go grab a copy of The Kansas City A's and the Wrong Half of the Yankees: How the Yankees Controlled Two of the Eight American League Franchises During the 1950s (the picture above is the cover from the book). No doubt it's an interesting read!