Complex sentence: Felix and Gladys Boldin owned the property since the early 60's and ran it as a tourist attraction up until he passed away in 1970 and his wife sold it to the state before her death.
Split into simpler sentences: Felix and Gladys Boldin owned the property since the early 1960's and ran it as a tourist attraction up until Felix died in 1970. Gladys sold it to the state before her death.