 They set cast iron monuments at the initial point on the boundary and every 10 miles along it as well as more frequent markings.A dispute in the late 1800s caused a portion of the line near Decatur County Iowa to be surveyed and re-marked with granite monuments every mile for 20 miles.In 2005 the State of Missouri contracted a resurvey of the border, locating the markers from the Supreme Court survey of 1850 and those added in the 1890s.