Trenton is a city in Grundy County, Missouri, United States. The population was 6,216 at the 2000 census. It is the county seat of Grundy County.

Trenton was first settled in 1834 and was known as Lomax Store for the J.S. Lomax General Store on a bluff above the Thompson Branch of the Grand River (Missouri). It was renamed Bluff Grove and won a battle with Tindall, Missouri to become the county seat of Grundy County, Missouri. The hilly area today is called the "Green Hills." It was renamed again in 1842 in honor of Trenton, New Jersey.

The Chicago and Southwestern Railroad (which became part of the Rock Island Line) arrived in 1869. In 1890 Avalon College, which had been founded in Avalon, Missouri by the United Brethern in 1869 moved to Trenton because of proximity to the railroad. The College nearly closed again.

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