I still believe Quartermaster Sergeant William E. Rosser, of Col. Tandy Walker's 1st Choctaw and Chickasaw Mounted Rifles, CSA, burned (perhaps with some help) the 100-foot span Iron Bridge of the Beale Wagon Road across San Bois Creek just northwest of the hamlet of Iron Bridge, Haskell County, Oklahoma. But the nagging question remains WHEN?
On June 27, 1864 at Limestone Prairie, C.N. Col. Stand Watie reports that to protect his withdrawal from Pleasant Bluff (Tamaha) following his capture of the Union steamboat J. R. Williams on June 15 and the arrival of reinforcements from the Chickasaw regiment, he sent a combined force of 150 men under Major Campbell east (from near Stigler) along the Beale Wagon Road to the Iron Bridge on the Sans Bois. Shortly after daylight (on about June 20, 1864) a small Union cavalry detachment coming west from Fort Smith arrived near the Iron Bridge and a small skirmish ensued. The Union force then brought up their artillery and a larger skirmish developed between the opposing artillery units. After a few volleys were fired, the enemy cavalry retreated back toward Fort Smith, taking their artillery with them.
Watie implies that the Iron Bridge across the Big San Bois was still useable about June 20, 1864. General Cooper had also sent Col. Tandy Walker's 1st Choctaw and Chickasaw Mounted Rifles to the area to protect Watie's retreat, but was not in the fight. Walker may have heard the artillery fire of the skirmish at the bridge, and arrived at the bridge shortly after the fight. Realizing the the Union cavalry may soon return from Fort Smith with a heavier force, Col. Walker may have ordered Sergeant William E. Rosser to burn the San Bois Iron Bridge as Watie retreated back to Limestone Prairie, C. N., as Sgt. Rosser said he did burn it. Thus it appears that Sgt. Rosser had a second opportunity to burn the Iron Bridge across the San Bois.
URLs of salient pages of the Official Records are:
https://babel.hathitrust.org/cgi/pt?id=coo.31924077700288;view=1up;seq=1033
https://babel.hathitrust.org/cgi/pt?id=coo.31924077700288;view=1up;seq=1034
https://babel.hathitrust.org/cgi/pt?id=coo.31924077700288;view=1up;seq=1035