The city was incorporated in 1987 when the communities
of Valencia, Saugus, Canyon Country, and Newhall were combined.
With regards to growth periods, Camus et al(2000) and Berthommier et al(1992)
include the Plawangan and Turgo hills to‘Ancient Merapi' where as Newhall et al(2000) suggest the hills are relics of‘Proto-Merapi'.