Complex sentence: The railroad then formed the Santa Fe Land Improvement Company to develop a planned community of country estates, and 6,200 acres developed from the original Rancho San Dieguito land grant were renamed "Rancho Santa Fe" in 1922.
Split into simpler sentences: The railroad then formed the Santa Fe Land Improvement Company to develop a planned community of country estates. A plan was adopted, and 6,200 acres developed from the original Rancho San Dieguito land grant were renamed "Rancho Santa Fe" in 1922.