The Act of Congress of July 6, 1785, established a national currency, the unit being a dollar, equal in value to the Spanish milled dollar. The Spanish milled dollar had been in circulation in this country for many years, and was the expressed unit in the paper money and other obligations, authorized by Congress since the first year of the Revolution. The United States mint, however, was not authorized until the passage of the Act of Congress of April 2, 1792, and the first coinage of silver and gold did not take place until two years later. During this interval the circulating medium was mainly Spanish silver money and the consideration mentioned in conveyances was usually in the Spanish milled dollar. In 1801, a lot having a front on Market Street of thirty feet and a depth of seventy feet, was sold for six hundred and twelve dollars and fifty cents; in 1803, a lot having a front of forty-six feet and a depth of seventy feet was sold for thirteen hundred dollars. In 1804, an undivided fourth interest in a lot having a front of fifty-six feet, and a depth of one hundred and seventy-five feet, was sold for eight hundred and seventy-five dollars. In 1805, a half interest in a lot also having a front of fifty-six feet, and a depth of one hundred and seventy-five feet was sold for twelve hundred dollars. In 1806, an eighth interest in a lot having a front of fifty-six feet, and a depth of one hundred and seventy-five feet, was sold for two hundred and seventy-five dollars. In 1807, a sixth interest in a lot having a front of fifty-six feet, and a depth of one hundred and seventy-five feet, was sold for six hundred and sixty-six dollars and sixty-six cents. Most of the houses were built on land leased from the owners, or on lots subject to the payment of ground rents, which accounted to some extent for the inferior quality of the improvements. The number of brick houses on Market Street was still so limited that the merchants were fond of referring to the fact that the establishments conducted by them were located in a “brick house” or “next door to,” or “across the street from,” a “brick house.”