Serving for several years at Fort Orange (present-day Albany, New York) on the upper Hudson River, he is credited with being the first Protestant missionary to the Indians in North America.
The minister is widely known as the author of A Short Account of the Mohawk Indians, their Country, Language, Figure, Costume, Religion, and Government, first published from his letters by friends in 1644 in North Holland, and being translated into English in 1792 and printed in Philadelphia.
In 1629 Megapolensis entered the ministry and commenced conducting services at Wieringerwaard, and four years later at Sehoorel and Berge in the Classis of Alkmaar.
In November, 1641, Domine Johannes Backerus introduced him to the Classis of Amsterdam with the idea that he was willing to pursue a pioneering effort as a minister in New Netherland at the patroon of Killiaen Van Renssear.
Upon their arrival at New Amsterdam they remained on Manhattan Island for a brief period where he was introduced to Reverend Everardus Bogardus, who was directed to extend a friendly welcome.
[5] With its strategic location Fort Orange and its nearby settlements soon attracted many traders and Indians alike, however, because of the many different peoples and interests it was also the center of many conflicts.
[11] Van Rensselae also needed someone he could trust to be his principle adviser and to keep him informed of the social and business activity in the manor.
[12] Megapolensis was given authority that extended further than matters of church and religion, and was appointed to act as the arbiter of all disputes arising between the chief official of the colony, Arent van Curler, and his subordinate, Adriaen van der Donck, and to see that the general patroon was dealt with in a fair and ethical manner.
[19] From his letters home, his friends in the Netherlands compiled A Short Account of the Mohawk Indians, their Country, Language, Figure, Costume, Religion, and Government, publishing it in North Holland in 1644.
[4] In his letters, Megapolensis had compared the land of Rensselaerwyck to that of Germany and described the rich abundance of game, birds and other wildlife.
He characterized the Mohawk ritual torture of captives as cruel, but noted that they seldom killed people in their culture, despite their lack of laws and authorities as he understood them.
[20] Megapolensis is widely noted for assisting French Catholic missionary Isaac Jogues escape captivity, when he was being held and tortured by the Mohawk Indians.
[22][d] In a letter of September 28, 1658, to the Classis of Amsterdam, Megapolensis wrote of the gruesome ordeal that had befallen Jogues, and another French missionary, François-Joseph Bressani, at the hands of the Mohawk.
[24] At the conclusion of his term of ministry at Fort Orange, Megapolensis planned to return to Holland, but was asked by Pieter Stuyvesant to become chief minister of the Dutch church in New Amsterdam.
[21] As dominie in New Amsterdam, Megapolensis was also responsible for mission stations in Bergen, New Jersey, the village of Haarlem, and occasionally in Brooklyn.
On March 18, 1655, he sent a letter to the Classis at Amsterdam, noting, “Last summer some Jews came here from Holland in order to trade... they came several times to my house, weeping and bemoaning their misery.
Megapolensis further argued that the followers of the “unrighteous Mammon” aimed to get possession of Christian property and to outdo other merchants by drawing all trade toward themselves.
These “godless rascals, who are of no benefit to the country, but look at everything for their own profit, may be sent away from here.”[29] After Stuyvesant's departure in July from his failed mission in the West Indies he returned to Manhattan and found a fleet and crews totaling seven-hundred men waiting for him in the harbor, where he promptly received orders to move on the Swedes at Fort Casimir and other objectives in the disputed territory along the Delaware River.
Reverend Backerus had retired over political indifference with Stuyvesant and returned to Holland and subsequently the colony was in need for another minister.
"[45] Susanah Shaw Romney says that his daughter Hillegond van Ruyven and Lydia de Meyer crossed enemy lines to Long Island to conduct back-door negotiations with the English.
Shortly after their return, "...a council of residents and colonial leaders presented Stuyvesant with English terms, and he finally empowered a group of Amsterdammers to negotiate the peaceful handover.
His role in the surrender may have had repercussions, as on two separate occasions years later, prominent Dutch citizens testified under oath to his loyalty to the West India Company.