The history of the Athletics Major League Baseball franchise spans the period from 1901 to the present day, having begun as a charter member franchise in the new American League in Philadelphia before moving to Kansas City in 1955 for 13 seasons and then to the San Francisco Bay in Oakland, California, in 1968 for 57 seasons. The team endured numerous attendance issues stemming from the aging Oakland Coliseum before the MLB owners approved the team's application to relocate to Las Vegas, Nevada in 2023. With four locations, the A's have had the most homes of any MLB team.

Philadelphia (1901–1954)

Beginning

The Western League was renamed the American League in 1900 by league president Bancroft (Ban) Johnson and declared itself the second major league in 1901. Johnson created new franchises in the east and eliminated some franchises in the west. Philadelphia was given a new franchise to compete with the National League's Philadelphia Phillies.

Former catcher Connie Mack was recruited to manage the club and persuaded Phillies minority owner Ben Shibe as well as others to invest in the team. The name of the team, Philadelphia Athletics, is a name taken from the 1876 NL Athletic Base Ball Club of Philadelphia.

Columbia Park was the Athletics first home. They played there from their founding in 1901 through the 1908 season, and it was the venue of their two home games in the 1905 World Series.

First dynasty and aftermath

In the early years, the Athletics established themselves as one of the dominant teams in the new league, winning the AL pennant six times (1902, 1905, 1910, 1911, 1913, and 1914), and winning the World Series in 1910, 1911, and 1913, led by its "$100,000 infield." They won over 100 games in 1910 and 1911, and 99 games in 1914.

In 1909, the Athletics moved into the major leagues' first concrete-and-steel ballpark, Shibe Park. This remains the second and last time in franchise history where a new ballpark was built specifically for the Athletics. In 1912, Mack bought the 25% of the team's stock owned by Sam Jones and Frank Hough to become a full partner with Shibe. Shibe ceded Mack full control over the baseball side while retaining control over the business side. However, Mack had already enjoyed a nearly free hand in baseball matters since the franchise's inception.

In 1914, the Athletics lost the 1914 World Series to the "Miracle Braves" in a four-game sweep. Mack traded, sold or released most of the team's star players soon after. In his book To Every Thing a Season, Bruce Kuklick points out that there were suspicions that the Athletics had thrown the Series, or at least "laid down," perhaps in protest of Mack's frugal ways. Mack himself alluded to that rumor years later but debunked it. He claimed that the team was torn by numerous internal factions and was also distracted by the allure of a third major league, the Federal League, which began play in 1914 and raided players from the AL and NL teams. Mack refused to match the upstart league's offers, preferring to rebuild with younger (and less expensive) players. The result was a swift and near-total collapse, as the 1914 pennant winning Athletics collapsed to a modern major-league low record of 36–117 (.235) in 1916. The team would finish in last place every year through 1922 and would not contend again until 1925. Shibe died in 1922, and his sons Tom and John took over the business side, leaving the baseball side to Mack, who for all intents and purposes, was now the head of the franchise, and would remain so for the next three decades.

Second dynasty (1927–1933)

By the latter half of the 1920s, Mack had assembled one of the most feared batting orders in the history of baseball, featuring three future Baseball Hall of Fame members, including Al Simmons, Jimmie Foxx, and Mickey Cochrane. A fourth future Hall of Fame member was pitcher Lefty Grove. In 1927 and 1928, the Athletics finished second to the New York Yankees, then won pennants in 1929, 1930 and 1931, winning the World Series in and . In each of the three years, the Athletics won over 100 games. While the 1927 New York Yankees, whose batting order was known as the Murderers' Row, are remembered as one of the best teams in baseball history, the Athletics teams of the late 1920s and early 1930s are largely forgotten. Opponents who faced both teams considered them to be generally equal. Both teams won three consecutive pennants and two of three World Series. Many veteran baseball observers believe that the Yankees' far more exalted status in history is due largely to the fact that they played in New York, where most of the national media is located. As it turned out, this would be the Athletics' last hurrah in Philadelphia. The Great Depression was well under way, and declining attendance drastically reduced the team's revenues. Mack again sold or traded his best players in order to reduce expenses. In September 1932, he sold Simmons, Jimmy Dykes and Mule Haas to the Chicago White Sox for $100,000. In December 1933, Mack sent Grove, Rube Walberg and Max Bishop to the Boston Red Sox for Bob Kline, Rabbit Warstler and $125,000. Also in 1933, he sold Cochrane to the Detroit Tigers for $100,000. The construction of a spite fence at Shibe Park, blocking the view from nearby buildings, only served to irritate potential paying fans. However, the consequences did not become apparent for a few more years, as the team finished second in 1932 and third in 1933.

Lean years Mack was already 68 years old when the Athletics won the pennant in 1931, and many felt that the game had long since passed him by. Although he had every intention of building another winner, he did not have the extra money to get big stars. He also did not (or could not) invest in a farm system. Unlike most other owners, Mack had no source of income apart from the Athletics, so the dwindling attendance figures of the early 1930s hit him especially hard.

As a result, the Athletics went into a decline that lasted for over 30 years, through three cities. The Athletics finished fifth in 1934, then last in 1935. Except for a fifth-place finish in 1944, they finished in last or next-to-last place every year through 1946. Tom Shibe died in 1936 and John succeeded him as club president. However, John resigned due to illness a few months later, leaving the presidency to Mack. When John died on July 11, 1937, Mack bought enough shares from the Shibe estate to become majority owner. However, Mack had been the franchise's number-one man since Ben Shibe's death. Even as bad as the Athletics got during this time, Mack retained full authority over business and baseball matters. Long after most teams hired a general manager, Mack continued making all personnel decisions and leading the team on the field. One of the few times that he even considered ceding some of his duties came in the 1934–35 offseason, when the Athletics were not far removed from what would be their last great era. He seriously entertained hiring Babe Ruth to succeed him as manager, but backed off from this idea, saying that the Babe's wife, Claire, would be running the team within a month. Even when the Phillies moved to Shibe Park as tenants of the Athletics midway through the 1938 season, not enough revenue came in for Mack to build another winner.

By the mid-1940s, as Mack passed his 80th birthday, he was showing unmistakable signs of mental deterioration, almost to the point of senility. He would frequently sleep through innings, make bad calls that his coaches simply ignored, have inexplicable fits of anger, or call players from decades earlier to pinch-hit. Mack also never installed a telephone in the dugout and instead would use a series of obtuse hand signs to signal his coaches on the field. For the most part, Mack's coaches handled in-game operations. Nonetheless, despite calls inside and outside the organization to step down, Mack would not even consider firing himself. Also, during this time, Mack gave minority stakes in the team to his sons, Roy, Earle and Connie Jr., with the intention to have all three of them inherit the team upon his death. He also intended for Earle, who had been assistant manager since 1924, to succeed him as manager. This decision would have dire consequences for the Athletics later on.

During this time, Shibe Park was also becoming an increasing liability. While the facility had been state of the art when it opened in 1909, by the late 1940s, it had not been well maintained in some time. It was also not suited to automobile traffic, having been designed before the Ford Model T was introduced.

Final years Surprisingly, in 1947 the Athletics finished with a winning record for the first time in 14 years. They contended for much of 1948, and most of the summer in either first or second place, though due to the firing of a number of pitchers, the team faded to fourth place by season's end. The franchise would not be a factor in a pennant race again at that late date until 1969—their second year in Oakland. Another winning record in 1949 sparked hopes that 1950—the 50th season for both the American League and Mack's tenure as manager of the Athletics—would bring a pennant at last. During that year, the team wore uniforms trimmed in blue and gold, in honor of the Golden Jubilee of "The Grand Old Man of Baseball." However, the 1950 season was an unmitigated disaster, as they were already out of contention by the end of May. Before May was out, Mack's sons had agreed to ease their father out as manager. On May 26, it was announced that Mack would resign at the end of the season. On the same day, former Athletics star Jimmy Dykes, who had returned to the Athletics as a coach a year earlier, was named assistant manager and would transition to manager for the 1951 season. However, for all practical purposes, Dykes took over as manager immediately; he was given control over the Athletics' day-to-day operations and became the team's main game-day operator. Cochrane, who had been brought back as a coach earlier in the year, was named general manager, stripping Connie Sr. of his last direct authority over baseball matters.Warrington, Robert D. Departure Without Dignity: The Athletics Leave Philadelphia. Society for American Baseball Research, 2010. Ultimately, the Athletics finished with the worst record in the majors at 52–102, 46 games out of first. Mack's 50-year tenure is a North American professional sports record for manager/head coach that has never been threatened. They would have only one winning record from 1951 to 1954—a fourth-place finish in 1952. The nadir came in 1954, when the Athletics finished with a ghastly 51–103 record, easily the worst record in baseball and 60 games out of first.

At the same time, the Phillies, who had been the definition of baseball futility for over 30 years, began a surprisingly quick climb to respectability. The Athletics were the more popular team in Philadelphia for most of the first half of the century, even though for much of the last decade they had been as bad or worse than the Phillies. But in the 1940s, the Phillies began spending lavishly on young prospects. The impact was immediate. In 1947, the Athletics finished fourth in the American League while the Phillies tied for the worst record in the National League. Just three years later, the Athletics compiled the worst record in the majors and the Phillies went all the way to the 1950 World Series. It soon became obvious that the Phillies had passed the Athletics as Philadelphia's number-one team.

Selling the team