DNR land surveyor Bob Vollmer linked modern surveying work to the earliest surveyors who walked the land in the 1800s. Land surveyors locate the elevation and position of property points, using distances and angles to create property maps and boundaries that determine legal ownership. Bob Vollmer, born in 1917 and pictured in 2017, was still working at age 100. Over more than 50 years as a DNR surveyor, he established boundaries for properties including this nature preserve to protect them from encroachment. During his tenure, surveying tools changed radically, from labor-intensive work that often required clearing vegetation for a clear line of sight to the use of GPS for calculations in seconds. The roots of this work lay in the Land Ordinance of 1785, which replaced an older surveying system with fixed north-south and east-west lines and established the townships and sections still used today, and in the Northwest Ordinance of 1787, which authorized settlement of the Indiana Territory. Early 1800s surveyors in the Indiana Territory recorded vivid notes about the landscape, including observations made here on December 6, 1819, and those notes are still used in planning for Indiana's protected lands. The 10 O'Clock Line Nature Preserve takes its name from an 1809 land treaty between General William Henry Harrison and Miami Chief Little Turtle, whose northern boundary crossed the preserve; according to tradition, the Miami distrusted the surveyor's equipment, so a spear was thrown into the ground at 10 o'clock and its shadow became the treaty boundary line.