The longest-running sitcoms in television history come from several different decades and have different styles of humor but have all left a lasting legacy. Sitcoms have always been a staple of television, as even classic golden age TV was known for shows like Father Knows Best and Leave it to Beaver gave way to even more groundbreaking sitcoms like All in the Family and The Jeffersons. However, when it came to sitcoms, lasting for 15 or 20 seasons was never easy as humor is subjective and changes over time. Yet some have shown incredible lasting power over the years.