NOAA Hurricane Re-analysis Project: 1969 Hurricane Camille.
Hurricane Camille is one of only three category 5 hurricanes to make landfall on U.S. coastline. At the time it was suggested, based on wind measuring instruments, that the maximum sustained winds were 190 mph. It had ranked as the strongest storm ever to hit the U.S. But, according to a group of researchers in Miami this is no longer true.
Using old ship reports and pouring over old satellite images, radar data and coastal radars, the scientists have determined that the winds were closer to 175 mph when it slammed into Mississippi on August 17th 1969.
With a better understanding of how these hurricane behave, and gaining experience from looking at thousands of images from satellites over the past 6 decades, this group from Florida University and the Hurricane Center are now ranking Camille as the 2nd strongest storm ever to strike the coast of the U.S.
Over the past 120 years of data, there have been only 3 category 5 storms to make landfall on the United States coastline. In 1935, a storm with winds of 185 mph moved through the Florida Keys, and hurricane Andrew on August 24th moved in on SE Florida, just south of downtown Miami. Andrew had winds of 165 mph. Interesting to note, that Andrews' winds were also changed several years later, after some tests were done on some of the wind measuring devices that underestimated the winds of this monster of a storm.
Here is a link to the actual study: http://www.aoml.noaa.gov/hrd/data_sub/re_anal.html