Complex sentence: It first signed on in 1925 and is primarily associated with the popularization of country music through its weekly Saturday night program the "Grand Ole Opry", the longest-running radio program in history, began as the "WSM Barn Dance" in 1925.
Split into simpler sentences: It first signed on in 1925 and is primarily associated with the popularization of country music through its weekly Saturday night program the "Grand Ole Opry". The longest-running radio program in history, began as the "WSM Barn Dance" in 1925.