Emerson High School was originally the sole high school to serve the municipality of West Hoboken, New Jersey. In 1925, West Hoboken merged with its neighbor to the north, Union Hill, New Jersey, which had been served by Union Hill High School, to form the city of Union City, New Jersey. As the city was now served by two high schools, students who lived north of the Route 495 overpass (which previously divided the two towns) would attend Union Hill, while those who lived south of it would attend Emerson, though that boundary was shifted in later years to keep the school enrollments roughly equal.