Complex sentence: The Anaheim Amigos became the Los Angeles Stars in 1968 and played at the Los Angeles Memorial Sports Arena until 1970, at which point the team moved to Salt Lake City, Utah, to become the Utah Stars.
Split into simpler sentences: The Anaheim Amigos became the Los Angeles Stars in 1968 and played at the Los Angeles Memorial Sports Arena until 1970. At which point it moved to Salt Lake City, Utah, to become the Utah Stars.