The plans prepared by the McMillan Park Commission and submitted, with its report, to the Senate, constituted the first and most notable proposal for grouping of public buildings ever put forward in the United States. The outlying sections of the District of Columbia were studied in relation to a system of parks, both large and small areas being indicated; the most convenient and the most picturesque connections between the various parks were mapped; the individual treatment which each important park should undergo was recommended; an extension of the park system to Great Falls and to Mount Vernon was discussed. Primarily, however, the development of the Mall received detailed and elaborate treatment, and the location of new public buildings, whether legislative, executive, or municipal in character, was arranged according to a rational system of grouping; and those memorials which mark distinct epochs in our national history were brought into harmonious relation with the general scheme of development. As a result of this study, the desirability of making every considerable undertaking within the District of Columbia a part of a general plan was made evident, so that each undertaking should contribute its part to enhancing the value of the whole; and no undertaking would be allowed to invade, to mutilate, or to mar the symmetry, simplicity, and dignity of the one great composition designed to comprehend the entire area. In working out the plans the park commission found it necessary to have prepared two models, one showing the existing disturbed conditions in the section from the Library of Congress westward to the Potomac, and the other showing the arrangement proposed. These models, constructed with the utmost attention to the details of topography by George C. Curtis, were accurate maps of the section they so graphically depicted, and served as guides in carrying the plans to completion. To present in graphic fashion particular features of the plans, the accurate architectural drawings were rendered in color by leading artists, and by means of these pictures a clear and distinct idea of the completed work was obtained. One of the greatest obstacles to a restoration of the Mall as provided for in the L’Enfant plan was the fact that since 1872 the Mall had been occupied by railroad tracks, the board of aldermen and the board of common council having on March 20, 1871, granted the Mall site to the Baltimore Potomac Railroad Co., later the Pennsylvania Railroad Co., which action was confirmed by act of Congress May 21, 1872. The Mall was then no better than a common pasture. The railroad had taken the place of the canal, which it paralleled, and held the right to use the property by a title good in law and in equity; also by virtue of an act of Congress adopted in 1890 the railroad space had been enlarged, in consideration of the surrender of street trackage and the proposed elevation of the tracks within the city of Washington.