After the extensive plague epidemics of 1679 and 1713, the population began to grow steadily. It is estimated that 150,000 people lived in Vienna in 1724, and 200,000 in 1790. At that time, the first factories were built, starting in Leopoldstadt. Leopoldstadt also became a site where many Jews lived, as they had been driven out of their 50-year-old ghetto in 1670. Hygienic problems began to become noticeable: sewers and street cleaning began to develop. Also in this time, the first house numbers (the "Konskriptionsnummern") were issued, and the government postal system began to develop.