The area was first developed following the Civil War when the streets between First and Second Avenues were largely built up with brownstone-fronted row houses erected for the middle class. Development of single-family houses in the Tudor City area peaked in 1870. Elevated railway lines were erected on Second and Third Avenues in the late 1870s, and soon afterward the blocks east of First Avenue were taken over by noxious industries: abattoirs and meat packing houses, a gasworks, and a glue factory. Middle-class families abandoned their row houses, which were converted into rooming houses or replaced by tenements. Prospect Hill became a multi-ethnic slum. At the same time, as a result of the increasing shortage of servants and the growth of the automobile industry, Manhattan's middle and upper classes began to flee to the suburbs. Many workers then commuted by train to the new Grand Central Terminal and the office buildings which sprang up around it.