Fence in LeDroit Park as shown in the 5/31/03 "Washington Times". Purported to be a remaining example of the fences built by developer A.L. Barber Co. to separate the then whites-only subdivision from the adjacent, largely black, neighborhood of Howard Town.
According to the Times, the fences were torn down in protest and rebuilt several times until a compromise was reached in 1901 and the bulk were removed. A bit more information (but with conflicting dates) is available in this New York Times article.