An Act of Congress in 1806 authorizing the National Road required mile markers at regular intervals to confirm the route and show distances traveled and remaining. Their use traced back to the Roman Empire, where stone obelisks first appeared in the fourth century B.C. along the Appian Way from Rome to Brindisi. Along the National Road, markers were set at 1 mile intervals on the north side, and while each state used a different design, all carried the same basic information. In Ohio they were square with round heads and made of early concrete, sandstone, or limestone, while in Pennsylvania they were cast-iron obelisks. Ohio's 5-foot markers were set 2 feet into the ground with 3 feet exposed. Each marker gave the distance from Cumberland, Maryland, where the Road begins, and named the nearest cities and villages for eastbound and westbound travelers. A standard pattern placed at the top the number of miles from Cumberland, on the next row the next large town and its distance, on the left the next town to the east, and on the right the next town to the west with the remaining miles. At the bottom, an initial and small number usually identified the nearest town, recognizable locally without spelling it out. By the 1920s, a uniform highway numbering system and standardized road signs had replaced the old mile markers, though many still remain along the Road.