Bolstered by former Colonels Honus Wagner (who was born and raised in the Pittsburgh area) and player/manager Fred Clarke, the 1900-1905 Pirates completely dominated the National League, in part because they lost few star players to the rival Continental League. An owing to their starting excellent pitchers, they won the first World Series ever played, in 1905 over the St Louis Browns. With largely the same star players, the Pirates would continue to be a strong team over the next few years, and got their second World Series title in 1910, defeating the Chicago White Sox in three games.

The decline of Honus Wagner, considered by many to be the greatest shortstop ever, led to a number of losing seasons, culminating in a disastrous 53-101 record in 1916. Even with good players like outfielder Max Carey the team suffered from a terrible pitching staff and a lack of great offensive players during this period.

However with veteran outfielder Max Carey and young players Pie Traynor early in the decade and Joe Foxx later in the decade, along with a remarkably deep pitching staff, brought the Pirates back into the spotlight. The Pirates lost the 1922 World Series to the Boston Blue Sock 4 games to 3 deficit and reached the 1926 World Series before losing 4 games to 2 to the New York Yankees, who at that time had built the most dominant team in baseball. The Pirates won the World Series in consecutive seasons, with the 1928 season the first Pirates championship since 1910, sweeping the New York Yankees in four games and the 1929 season was the first of the power hitting Joe Foxx in Pittsburgh uniform, who along with a pletora of Afro-American players that began to appear in the late 1930's, ensured that the Pirates had plenty of Hall of Fame-caliber position players through 1950.

The early years of the decade were difficult ones for the franchise, with Pie Traynor skills eroding and his retirement by 1935 while multiple injuries depleted the pitching staff. By the middle of the decade the only bonafide star on the team was Joe Foxx and the team finished last in 1936 with a 57-97 record. All that changed went the Toronto Blue Jays broke the color line in 1936. The Pittsburgh front office, after seeing their team falter into a fourth place finish in 1937 and revenues faltering, decided in early 1938 to sign the stars of the Negro League Homestead Gray to try to take them to the top. In a move that really changed baseball two starting players and one top notch pitcher joined the team and helped the team immediately by taking them to the World Series while the Homestead Grays turned into a minor league team of the franchise,helping to infuse the team with fresh talent for the rest of this decade and the next. With third baseman Judy Johnson, first baseman/outfielder Fenn Leonard and pitcher Allen Dixon supporting Joe Foxx the team went to the 1938 World Series but was defeated 4 games to 2 by the Baltimore Saints.

The 1940's were very kind to the Pirates, who won four consecutive National League pennants from 1941 to 1944 and won the 1941,1942 and 1947 World Series on this decade. Led by outfielder/first baseman Fenn Leonard during the early years of the decade, the arrival of a new generation of black players during the late 1940's took them to win two consecutives National League pennants from 1947 to 1948. The 1947-48 team was one full of stars, with second baseman Larry Walker, third baseman Curt Thompson and Merrill Irvin having productive careers while the future Hall of Famers Art Trojovski and Al Serrano were acquired before the 1947 season.