As a matter of fact, perhaps the most unusual and original feature of the L’Enfant plan was the idea of building the city about two coordinate axes of parks--one a park system nearly a third of a mile wide, leading from the Capitol westward to the Potomac River, and the other the same width, leading from the White House south to the river, with the Washington Monument at their intersection. This was an innovation and a departure from the usual development of a city about a commercial street--a main street or a market street. Provision was made in the plan for such a great commercial street on the diagonal of the triangle, the avenue joining the Capitol with the White House, and named Pennsylvania Avenue, for the State in which the Federal Government had up to then spent the greater part of its life. Much of the Mall leading westward from the Capitol was unfortunately taken up by the estuary of Tiber Creek, which overflowed at high tide. It was the intention of Major L’Enfant and his urgent recommendation that this creek be confined to a canal which he proposed to construct along the northern part of the proposed park. This canal would not only afford water transportation for heavy and bulky materials to and from the business part of the city but at the same time would be a water feature of the proposed park. Unfortunately, while the canal was built, Tiber Creek was not entirely confined to it, and its estuary was allowed to continue to overflow the Mall area and thus delay its development. When the Washington Monument was located, instead of being placed at the exact intersection of the two park axes, it was placed on a natural hill near by which was safely above tide level. The idea of an avenue from the Capitol to the Washington Monument seems to have been abandoned for many years, and when the Smithsonian Institution was built in the Mall the plan made by A. J. Downing was adopted for the entire Mall, superseding that of L’Enfant. These were the days when the so-called naturalistic park development was in vogue, and everything had to be consciously picturesque. No road or path could be straight, and no regularity in planting or plan was tolerated. The L’Enfant plan was again disregarded in laying out the Department of Agriculture grounds in 1867. With the avenue of the Mall out of the picture, there was no reason apparent to those in authority for refusing permission to the Pennsylvania Railroad Co. to run its tracks across the Mall and build its passenger station in the Mall itself, at Sixth Street.