 The Blackwater fire was started by a lightning strike on August 18 , 1937 , but it remained undetected until early August 20 , at which time it was estimated to be about 2 acres ( 0 @.@ 81 ha ) in size . By the evening , it had expanded to 200 acres ( 81 ha ) , and 65 firefighters from the United States Forest Service ( USFS ) , which included CCC company 1852 from the Wapiti Ranger District of Shoshone National Forest and employees of the Bureau of Public Roads ( BPR ) , were constructing fire lines along two flanks of the fire . A gas @-@ powered portable pump was delivered and set up using water from Blackwater Creek by midnight . Another pump arrived after that and firefighters installed 2 @,@ 000 ft ( 610 m ) of hose line on the north flank of the fire and another 5 @,@ 000 ft ( 1 @,@ 500 m ) on the west flank . CCC workers from the National Park Service arrived at 2 : 30 am on August 21 and started construction of fire line along the north flank of the fire . Meanwhile , increasing winds had begun expanding the fire to the east . 
