The Dutch city of New Amsterdam, which became New York by the English conquest in 1664, was of slow growth. It had hardly more than twenty thousand inhabitants at the time of the Revolution, being less than either Boston or Philadelphia, and a map made in 1767 shows that the town scarcely extended beyond Wall Street. At the beginning of the nineteenth century there were sixty thousand people, and its rapid growth began through large immigration after the War of 1812, and was stimulated by the completion of the Erie Canal in 1825, which gave it greatly increased foreign trade. By the new Charter of "Greater New York" coming into operation in 1897, the city was made, next to London, the largest in the world, being expanded beyond Manhattan Island, so as to include all the outlying cities. It now consists of five boroughs, Manhattan, the Bronx, Brooklyn, Queens and Richmond, having an area of three hundred and twenty square miles, and a population exceeding three and one-half millions. If Jersey City and the other New Jersey settlements on the west side of the Hudson were added, the population would be four millions. This great city is about thirty-five miles long from north to south, and nineteen miles wide. The long and narrow island of Manhattan stretches thirteen miles, while it is not much over two miles broad in the widest part, and sometimes narrows to a few hundred yards, particularly in the northern portion. The Harlem River and the winding strait of Spuyten Duyvel separate northern Manhattan from the mainland. The island is very rocky, excepting the southern part, which is alluvial, and at the upper end the cliffs rise precipitously from the Hudson over two hundred and thirty feet into Washington Heights, and the surface descends sharply on the eastern side to the Harlem flats. It does not take the visitor long to recognize, however, that the capacious harbor, the converging rivers and numerous adjacent arms of the sea combine all the requisites of a great port, and they could not have been better planned if human hands had fashioned them. There is a vast wharf-frontage, for over fifty miles of shore-line are available for shipping, thus accommodating an almost limitless commerce. This has made the metropolis and continues its wonderful growth.