The House of Flanders, also called the Baldwins, was a medieval ruling family of Frankish origin that was founded by Baldwin Iron Arm, son-in-law of Charles the Bald. The House of Flanders was the first dynasty to transform a county function of the Carolingian Empire into a hereditary fiefdom, the County of Flanders, falling under West Francia, created by the Treaty of Verdun in 843.