Mamanto was a sachem from Massaco (Simsbury) and one of the principal leaders of the Connecticut River Indians.  In 1661, he and two other Indians sold their rights to Weatogue meadow and lands adjacent to the English, reserving two acres of planting land.  Four years later in the fall of 1665, he was sued by a man named Lord for a debt and forced to pay twenty-five bushels of corn in damages.
By 1673, the Massaco leader had not been provided his two acres as stipulated in the former agreement.  After Mamanto brought the matter before colonial authorities, the Court of Assistants on May 6, ordered that the marshal speedily lay out two acres of good planting ground near Farmington bounds and mark it out by meer stones.  A few weeks later on May 22, Mamanto and his wife were among those Massaco who signed a confirmatory deed to Farmington. As the tensions in Southern New England Indian Country increased prior to the outbreak of King Philip's War, Mamanto joined other prominent leaders from the River communities -- Joshua Uncas, Matchisaps, Nesaheagen, Wequogan -- in assisting the colonial army. 
In post-war Connecticut, Mamanto's wife placed her name with other Massaco on a 1680 deed to Simsbury.  However, they did not receive compensation until two years later when she was given a coat and an amount of corn as payment.  Six years later, Mamanto others from Massaco alerted the Connecticut General Assembly that Seacut's widow and her brother Pussuk were selling Podunk land belonging to the petitioners and requested a guardian to prevent any other alienation of Podunk territory without adequate review. The last mention of Mamanto in the historical record was in 1689 when he provided a list of Indians in Farmington that were not members of the Tunxis but from other tribes -- Cowesuck, 
Margaret Wickens Pearce, Native and Colonial Mapping in Western Connecticut Land Records, 235. Ullman, Hartford County, County Court Minutes, 55. Farmington Papers, Connecticut Historical Society.  Phelps 1845: 148-150.  Additional sources for this biography come from the Related Digital Heritage Items listed below.