At one point in history, the United States had upwards of 14,000 wooden covered bridges. Most of them were built between 1825 and 1875 to cross a stream or river and were intended to withstand the elements. An uncovered wooden bridge may have a life span of only about 20 years while a covered bridge could stand for more than 100. Even still, they don't fare well without upkeep and restoration costs can be high. That's why iron replaced wood as the preferred bridge-building material in the mid-1800s. These days, fewer than 900 of the original wooden covered bridges are believed to still be standing. The A. M. Foster Bridge, seen in today's photo, can be found in Cabot, Vermont.