Abraham Isaacs op den Graeff, also Op den Graff, Opdengraef as well as Op den Gräff was one of the so-called Original 13, the first closed group of German emigrants to North America, and an original founder of Germantown, Pennsylvania, as well as a civic leader, member of the Pennsylvania Provincial Assembly, award-winning weaver, and as an early abolitionist signer of the first organized religious protest against slavery in colonial America. He, or his brother Derick op den Graeff, are briefly mentioned in John Greenleaf Whittier's poem "The Pennsylvania Pilgrim" simply as "Op Den Graaf".

Mennonites are a group of Anabaptist Christian communities tracing their roots to the epoch of the Radical Reformation. The name Mennonites is derived from the cleric Menno Simons (1496–1561) of Friesland, part of the Holy Roman Empire, present day Netherlands. Menno Simons became a prominent leader within the wider Anabaptist movement and was a contemporary of Martin Luther (1483–1546) and Philip Melanchthon (1497-1560). Through his writings about the Reformation Simons articulated and formalized the teachings of earlier Swiss Anabaptist founders as well as early teachings of the Mennonites founded on the belief in both the mission and ministry of Jesus. Formal Mennonite beliefs were codified in the Dordrecht Confession of Faith (1632), which affirmed "the baptism of believers only, the washing of the feet as a symbol of servanthood, church discipline, the shunning of the excommunicated, the non-swearing of oaths, marriage within the same church", nonresistance, and in general, more emphasis on "true Christianity" involving "being Christian and obeying Christ" as they interpret it from the Holy Bible.