Complex sentence: In 1911, the National Society Daughters of the American Revolution (NSDAR) established a national committee known as the National Old Trails Road Committee whose work was, primarily, to definitively establish the Old Trails Road as a great National Memorial Highway.
Split into simpler sentences: In 1911, the National Society Daughters of the American Revolution (NSDAR) established a national committee known as the National Old Trails Road Committee. It worked to establish the Old Trails Road as a great National Memorial Highway.