In the 1980s and 1990s, first-division professional soccer leagues in the United States, such as the North American Soccer League and Major League Soccer, primarily used American football fields, many of which were oversized in terms of seating capacity and undersized in terms of the width of the soccer field; they often used artificial turf (none of which, at the time, were approved for international soccer under FIFA rules). Although many of the baseball parks had smaller capacities, natural grass, and a wider field, these parks were generally in use during summer, when North American–based soccer leagues, such as Major League Soccer, also hold their seasons, and the irregular field dimensions and sightlines were often considered undesirable.