I came across this flower in a field in Hodgenville, Kentucky. What makes Hodgenville particularly famous is that President Lincoln was born there.
After doing some Internet research (image databases are great!), I determined this is a musk or nodding thistle (Carduus nutans). The plant was introduced to North America from Europe in the mid to late 1800s. It is considered a weed in Kentucky and hampers hay production and animal grazing. This first image is of the flower missing from the plant, this shows the base area of the bloom.