The use of obscurants is a common practice by militaries worldwide. One of the most effective of these is white phosphorus (WP). WP is the elemental form of phosphorus that does not occur in nature and is highly toxic. The use of WP rounds on training ranges has led to a number of die-offs of grazing land animals and dabbling waterfowl, the first recorded in 1930. In the 1980s, thousands of waterfowl were dying annually at an impact range in Alaska, leading to the first large-scale investigation of WP as a lethal range contaminant. Tests were conducted at an upland impact range in New York to determine the quantity and persistence of WP in a typical environment. At all sites cited in this paper, WP was persistent for months to years following the detonation of WP munitions. At the Eagle River Flats range in AK, WP was identified from rounds fired in the 1950s, persisting over 45 years in a non-saturated environment. In New York, dispersal of gram quantities of WP occurred at detonation, and high concentrations of WP were found in the detonation craters a year after firing. Caution needs to be exercised when using white phosphorus munitions on ranges.