Peter Carl Johann von Rosenberg, soldier of Waterloo and pioneer of Texas, son of Otto and Maria (von Stempel) von Rosenberg, was born at Eckitten Estates, near Memel in East Prussia, on October 2, 1794. Little information is available on his early life and education. He enlisted in the Prussian Army at an early age and became a lieutenant in the cavalry at twenty-one. He fought with Blücher in the defeat of Napoleon at the Battle of Leipzig and later at Waterloo. In 1819 he inherited Eckitten Estates on the death of his widowed stepmother, and the same year he married Johanna Dorothea Frölich. They had four children before she died in 1826. In 1830 Rosenberg married Amanda Fallier (see ROSENBERG, AMANDA VON), by whom he had five more children. They also adopted his niece, Libussa Frölich. In June 1849 Rosenberg's eldest son, Carl Wilhelm von Rosenberg, a royal architect, was proscribed because of his outspoken democratic ideas and was barred from further employment with the government. He thus decided to emigrate to Texas. When Carl was unable to dissuade his son, he concluded that the entire family should emigrate together. Carl's brother Ernst was one of the first Germans in Texas with the Long expedition of 1821 and was killed in Mexico in 1826.
In October 1849 the family sailed from Bremen aboard the Franziska; they landed in Galveston in early December and traveled by mail coach and wagon down the coast to the mouth of the Brazos River. There they boarded the Washington and sailed up the Brazos to San Felipe de Austin. Carl and Wilhelm traveled to Bastrop and La Grange seeking to purchase a farm. Carl purchased the manor and 800 acres of Nassau Farm, a plantation in Fayette County which had been owned by the Adelsverein. Carl and Amanda prospered on the farm and stayed there until all the children were grown. In 1861 they moved to a small home in Round Top, where Carl stayed after Amanda's death in 1864. Rosenberg was a Freidenker (freethinker), and in his letters back to friends in Europe, he often wrote of the freedom he and his family enjoyed in Texas and America. Near the time of his death, he stayed with his daughter, Caroline Meerscheidt, in La Grange. He died of typhoid fever in La Grange on October 19, 1866.