Hi Carol:
     You wrote "They (African Americans) built the streets in the 19th
century, in order to stop the spread of malaria..." Exactly when did they
actually do this? To the best of my knowledge, the first person to describe
the parasite and its link to malaria was Alphonse Laveran, in 1880, in
Algeria. It was not until the 1890s when English, Italian and German
researchers pretty much figured out the life cycle with mosquitoes. Americans
joined in, during the building of the Panama Canal.
     Bricks are a lot like cobblestones - they were used when horses were the
primary mode of transportation. Actually, the best pavement for horses was
wood - boards laid end grain up (butt end) - as was done in 19th century
Berlin and other European cities. In Europe, cobblestones have been used for
centuries. The stones are laid in compacted sand or crushed stone. When road
work has to be done, the stones are removed, the work accomplished, and then,
the stones are replaced. This has been standard operating procedure for a few
centuries.
     Trolley tracks - I am assuming that few foundries in 19th century
America could produce them, probably more in the 20th century. Please note,
in New York City, trolley tracks - many laying beneath asphalt streets -
contain rare metals. The scrap metal value of trolley tracks is VERY high.
Russell A. Rudzwick