west union is an unincorporated community in washington county, oregon, united states. founded in 1851, the community had the first school district in the county, and it contains the oldest cemetery in the state and the oldest baptist church west of the rocky mountains. it is located north of hillsboro near the intersection of west union road and cornelius pass road north of the sunset highway. the name comes from a grove of five oak trees that was used as a meeting place of early settlers, or the "union of the west." west union had a post office from 1874 to 1894.