Complex sentence: The mining town of Union existed from 1887-88 in the area currently referred to as Deer Valley (also near the Union Hills which bear its name), but soon declined and left only a few ruins, making it a ghost town.
Split into simpler sentences: The mining town of Union existed for a few decades beginning in the 1880s in the area currently referred to as Deer Valley (also near the Union Hills which bear its name). It eventually declined and left only a few ruins, making it a ghost town.