Complex sentence: By the turn of the 20th century, Arcadia had a population nearing 500 and an economy that was becoming based on entertainment, sporting, hospitality and gambling opportunities; the latter including an early version of the Santa Anita race track.
Split into simpler sentences: By the turn of the 20th century, Arcadia had a population nearing 500 and an economy that was becoming based on entertainment, sporting, hospitality, and gambling opportunities. The latter including an early version of the Santa Anita race track.