Houses built between 1965 and 1972 may have aluminum wiring.  In 1974, two persons died in a home fire caused by faulty aluminum wiring. 

The main problem with aluminum wiring is a phenomenon known as
"cold creep". When aluminum wiring warms up, it expands. When
it cools down, it contracts. Unlike copper, when aluminum goes
through a number of warm/cool cycles it loses a bit of tightness each
time. To make the problem worse, aluminum oxidises, or corrodes
when in contact with certain types of metal, so the resistance
of the connection goes up. Which causes it to heat up and corrode/
oxidize still more. Eventually the wire may start getting very hot,
melt the insulation or fixture it's attached to, and possibly even
cause a fire.

After an extensive investigation of the cause of the fire, the  US Consumer Product Safety Commission  issued  Publication 516, REPAIRING ALUMINUM WIRING . Aluminum wiring is typically marked with the word ALUMINUM or the symbol AL.  Aluminum wiring is a very shiny silver and should not be confused with a tin/copper wire that has a very dull silver finish to it. Since most homes initially wired with aluminum wiring have had additional wiring installed, it is important to examine the labeling on the wiring.