First influence consists of topographical faults, i.e., water surfaces or sharp variations from levels. - Characteristics of platted cities, straight streets at right angles, permitting free movement throughout. - Characteristics of haphazard growth, irregular tangle of crooked and narrow streets preventing quick access to business center. - Some early plats attempt to forestall later needs and some to determine center of city. - Normal sizes of streets, alleys, blocks and lots: percentage of public and private land. - Unit from which plat built up.

The first step in studying the ground plan of cities is to note the topographical faults which normally control the shape of cities, by interfering with their free growth in all directions from their points of origin. These are of two kinds; water surfaces, such as harbors, lakes, rivers, creeks and swamps, or sharp variations from the normal city level, such as steep hills, deep hollows and ravines.

Water surfaces may either leave islands on which a city originates, as with New York and Galveston; promontories at the mouths of rivers, as with Boston and Portland, Me.; promontories between two rivers, as with Philadelphia and Pittsburg, or may consist of lakes scattered through the city's site, as with Minneapolis, Seattle and Grand Rapids; of rivers, as at Fort Wayne and Dayton; creeks, as at New Haven and Toledo; or marshes, as at New Orleans and Savannah. The rivers may have either a straight front, as at Albany, St. Paul and Portland, Ore., a curved front leaving a convex site, as at Cincinnati, Louisville and Memphis, or may be combined with small rivers and creeks intersecting the city's site in various ways. The deep harbors, lakes and rivers cannot be filled in, so that as far as they extend they furnish an outline for the city. Increasing demand for land, however, may project growth across the deep water surfaces and form suburban settlements beyond them. The power of rivers to hold growth on the side where the city originates depends on their width, on the area and relative advantages of the sites on the two sides of the river, and on speculative enterprise. At St. Louis, New Orleans and Kansas City, where the river is wide and the land across the river not attractive, the river forms practically an absolute bar to growth. At Toledo, Portland, Ore., Cincinnati, Pittsburg and Des Creeks are of chief importance when their erosion has worn a deep and wide ravine, the difference in level constituting a bar to a city's growth rather than the creek itself. When the creek is narrow it is frequently covered over and ceases to exert any influence, as in New York, Richmond, and other cities.

Philadelphia, 1682. Old plat shows central square, now the municipal center.

Philadelphia, 1682. Old plat shows central square, now the municipal center.

Plan of City, showing Buildings.

Plan of City, showing Buildings.

New Orleans, about 1728. Old French city; canal on the west later became Canal St., and American city built west of it.

Moines, many bridges connect the two sides and minimize the deterring effect of the river.

Swamps limit growth, for example preventing Philadelphia from growing south, and Savannah from growing east and west. On the other hand, New Orleans is largely built on a swamp, important parts of Washington and Syracuse were formerly swamps, and in the lower part of New York the Collect Pond, Lispenard Meadows, Beekman Swamp, etc, have been filled in and obliterated.

Example of platting parallel to irregular water fronts. Baltimore.

Example of platting parallel to irregular water fronts. Baltimore.

After a city has spread over the original levels and climbed some moderate elevations, the demand for land may cause a filling in of the lower levels. In Boston the Back Back district was created by filling; in Chicago, after the great fire of 1871, the city was raised from seven to ten feet; in San Francisco from Montgomery Street east was formerly mud flats; and the process of filling in land for business purposes continually goes on in the majority of water front cities.