Musical theatre evolved in the early 20th century as songwriters integrated music more fully into the plot and character development. Shows like Show Boat and Oklahoma used song to advance the story and provide insight into characters. These shows addressed serious themes through music and helped establish the modern musical. Later musicals in the 1950s by Leonard Bernstein continued innovating the form by incorporating newer musical styles into shows like West Side Story. Musical theatre then became more of an elite form of entertainment as other media like films rose in popularity.