There is only one place in the United States where four states come together: the four corners area in the western United States. At a barren, desert location, the states of Utah, Colorado, Arizona, and New Mexico share a common point. Due to surveying inaccuracies in 1875, the coordinates of the junction are 36.999 degrees north latitude and 109.045 degrees west longitude. The image covers an area of 16.3 by 17.6 kilometers, and was acquired on June 11, 2001.
Note: Although I lived in Arizona for 20 years, I have never visited the Four Corners Monument. However, with the help of Wikipedia and Google Maps, I can give some information about the above picture and the exact location of the four corners. First, the river that flows through this picture is the San Juan River, which flows from the southeast to the northwest (north is up in this photo). The long thin line that runs from the south toward the northeast is US 160. South of the river, there is a very fine black line (a road) that extends toward the northwest from US 160; the end terminus of that line is the Four Corners Monument. Colorado, of course, is to the northeast, New Mexico to the southeast, Utah to the northwest and Arizona to the southwest.
Photo credit: NASA/GSFC/METI/ERSDAC/JAROS, and U.S./Japan ASTER Science Team