Originally called Marshall Ford Dam, the name was changed in 1941 in honor of United States Representative J.J. Mansfield. The reservoir behind Mansfield Dam is named Lake Travis.
This site has pictures taken during the construction of Mansfield dam.
The following picture was taken using the High Dynamic Range (HDR) technique. HDR is a set of techniques that allows a greater dynamic range of luminances between light and dark areas of a scene than normal digital imaging techniques. The intention of HDR is to accurately represent the wide range of intensity levels found in real scenes ranging from direct sunlight to shadows.
TutorialBlog has rounded up numerous HDR tutorials in one place. So if you are interested in this technique, I recommend that you check it out. Have fun!