Please read the following table in Markdown format and then answer the question according to the table. Table cells in one row are seperated by '|', and different rows are seperated by '
'.

Table:
| Team | Sport | League | Established | Began in St. Louis | Venue | Championships in St. Louis | Left St. Louis |
| --- | --- | --- | --- | --- | --- | --- | --- |
| St. Louis Stampede | Arena Football | Arena Football League | 1987.0 | 1994.0 | Scottrade Center | 0 | 1995.0 |
| St. Louis Browns | Baseball | American League | 1894.0 | 1902.0 | Sportsman's Park | 0 | 1954.0 |
| St. Louis Stars | Baseball | Negro American League | 1937.0 | 1939.0 | Stars Park | 0 | 1939.0 |
| St. Louis Terriers | Baseball | Federal League | 1914.0 | 1914.0 | Handlan's Park | 0 | 1915.0 |
| St. Louis Maroons | Baseball | National League | 1884.0 | 1884.0 | Union Base Ball Park | 0 | 1886.0 |
| St. Louis Stars | Baseball | Negro National League | 1922.0 | 1931.0 | Stars Park | 3 (1928, 1930, 1931) | 1931.0 |
| Spirits of St. Louis | Basketball | American Basketball Association | 1967.0 | 1974.0 | St. Louis Arena | 0 | 1976.0 |
| St. Louis Hawks | Basketball | National Basketball Association | 1946.0 | 1955.0 | Kiel Auditorium | 1 (1958) | 1968.0 |
| St. Louis Bombers | Basketball | National Basketball Association | 1946.0 | 1950.0 | St. Louis Arena | 0 | 1950.0 |
| St. Louis Cardinals | Football | National Football League | 1898.0 | 1960.0 | Busch Stadium | 0 | 1988.0 |
| St. Louis All Stars | Football | National Football League | 1923.0 | 1923.0 | Sportsman's Park | 0 | 1923.0 |
| St. Louis Gunners | Football | National Football League | 1931.0 | 1931.0 | St. Louis National Guard Armory | 0 | 1934.0 |
| Missouri River Otters | Hockey | United Hockey League | 1991.0 | 1999.0 | Family Arena | 0 | 2006.0 |
| St. Louis Eagles | Hockey | National Hockey League | 1917.0 | 1934.0 | St. Louis Arena | 0 | 1936.0 |
| St. Louis Ambush | Indoor Soccer | National Professional Soccer League | 1984.0 | 1992.0 | St. Louis Arena / Scottrade Center | 1 (1995) | 2000.0 |
| St. Louis Steamers / St. Louis Storm | Indoor Soccer | Major Indoor Soccer League | 1977.0 | 1979.0 | St. Louis Arena | 0 | 1992.0 |
Question:
What year did Negro American League join?
Answer:
1939.0