Complex sentence: Growth was rapid, and San Dimas soon became an agricultural community, wheat and other Midwestern United States crops were planted first, then orange and lemon groves covered the town and the San Gabriel Valley.
Split into simpler sentences: Growth was rapid, and San Dimas soon became an agricultural community. Wheat and other Midwestern United States crops were planted first; then orange and lemon groves covered the town and the San Gabriel Valley.