Jefferson Street Grounds was a baseball field located in Philadelphia, Pennsylvania. It was also known as Jefferson Park and Athletics Park. It was home to three different professional baseball teams, competing in three different leagues. Notably, it was the venue for the first game in National League history, played on April 22, 1876. History Baseball had first been played on the site in 1864. Several local clubs held their games there, including the historic Olympic Ball Club of Philadelphia, which had begun playing various varieties of town ball starting in the early 1830s and had adopted the "New York game" by 1860. When they began playing at the Jefferson site, the diamond was situated at the southeast corner, at 25th (first base) and Master (third base). The Olympics built a clubhouse along Master. Jefferson was behind right field. Local newspapers typically gave the ballfield location as "25th and Jefferson". The grounds would be home to three different professional teams: Athletic Club of Philadelphia (also known as the Philadelphia Athletics) from 1871 to 1876. The team competed in the National Association until 1875, and in the National League of Base Ball Clubs in 1876. Philadelphia Base Ball Club (also known as the Philadelphia White Stockings) from 1873 to 1875, when they shared the venue with the Athletics. The White Stockings competed in the National Association. Philadelphia Athletics from 1883 to 1890. This franchise competed in the American Association. 25th and Jefferson, 1864 to 1875 The grounds were located on a large block bounded by Jefferson Street (north); 25th Street (east); Master Street (south); and 27th Street (west). Across the street to the south was the Spring Garden Reservoir, which has since been filled in. Although often listed as one ballpark, the 1870s diamond was located in the opposite corner of the block from the 1880s diamond. The facility opened to professional league baseball during 1871, as early as May 15. The club's first official National Association home game was played on June 3. The seating capacity was meager, only 5,000 seats. The inaugural National League game was played there, on Saturday, April 22, 1876, between Athletic and Boston; the Bostons won, 6–5. By a quirk of fate, it was the only National League game played that day, all others being rained out. This game is often pointed to as the beginning of Major League Baseball. 26th and Jefferson, 1883 to 1890