 MD 23 is a part of the National Highway System as a principal arterial from US 1 in Hickory west to High Point Road west of Forest Hill.The first section of MD 23 to be paved was the part of the Old York Turnpike from MD 138 to MD 439, which was improved as a macadam state-aid road by 1910.The portion of MD 23 from Hickory to Jarrettsville was designated one of the original state roads by the Maryland State Roads Commission in 1909.