From Wikipedia:
"United States
As of September 2007, most on-highway diesel fuel sold at retail locations in the United States is ULSD.
Ultra-low sulfur diesel fuel was proposed by EPA as a new standard for the sulfur content in on-road diesel fuel sold in the United States since October 15, 2006, except for rural Alaska. California has required it since September 1, 2006, and rural Alaska will transition all diesel to ULSD in 2010.
This new regulation applies to all diesel fuel, diesel fuel additives and distillate fuels blended with diesel for on-road use, such as kerosene, however, it does not yet apply to railroad locomotives, marine, or off road uses. By December 1, 2010, all highway diesel fuel will be ULSD.
Non-road diesel fuel was required to move to 500 ppm sulfur in 2007, and further to ULSD in 2010. Railroad locomotive and marine diesel fuel also moved to 500 ppm sulfur in 2007, and will change to ULSD in 2012.
There are exemptions for small refiners of nonroad, locomotive and marine diesel fuel that allow for 500 ppm diesel to remain in the system until 2014. After December 1, 2014 all highway, nonroad, locomotive and marine diesel fuel produced and imported will be ULSD."