managing the springfield herald ink problem Solution Summit is a city in Union County, New Jersey, United States. At the 2010 United States Census, the city\'s population was 21,457. Summit had the 16th-highest per capita income in the state as of the 2000 Census. What is now the city of Summit was created as Summit Township by an Act of the New Jersey Legislature on March 23, 1869, from portions of New Providence Township (now Berkeley Heights) and Springfield Township. Summit was reincorporated as a city on March 8, 1899.