The Long Walk was commenced by Charles II from 1680-1685 by planting a double avenue of elm trees. The central carriage road was added by Queen Anne in 1710. The original planting comprised 1,652 trees placed 30 feet apart in each direction. The width between the two inner rows was 150 feet, and overall 210 feet. It is a little less long than the three miles of popular rumour being around 2.65 miles (2 2/3rds miles or 4.26 km) from George IV Gateway at Windsor Castle to The Copper Horse.
In 1859 a Commission, of which the Duke of Bedford was President, inspected the Long Walk, and recommended (“…after mature consideration…”) that the old trees, when dead, dangerous, or decayed, should be gradually replaced by young elms between the Castle and the Double Gates, adjacent to Park Street, but from that point to the Statue of George III on Snow Hill, the soil proved unsuitable for elms and so there should be a gradual substitution of oak for elm in that part of the avenue. This plan was therefore adopted on a small scale in 1861, when a small enclosure was planted with oaks on the east side in the line of the Avenue. In 1879, three other enclosures were formed on the same principle, one either side of Snow Hill, and another opposite the plantation created in 1861.
Elms were felled and replaced with Horse Chestnut and London Plane working north from the Copper Horse end, significant work being undertaken in 1921 and in the early 1930s at which time the decision was made to widen the distance between the lines of trees on each side of the avenue.