Beginning with the Whitman Massacre in November 1847, chapters cover campaigns against the Cayuse in 1848 and the Yakimas in 1855-56. The Oregon Rifles and the Oregon Mounted Volunteers had prominent roles in these campaigns and the U.S. regular forces that were present were often commanded by men who would later gain fame in the Civil War. The 1858 Steptoe-Wright expeditions from Ft. Walla Walla to what is now the Washington-Idaho border region are also described. During these campaigns, several other temporary forts were constructed. Ft. Walla Walla became an important strategic post and during the Civil War years was garrisoned by various volunteer regiments from California (2nd Volunteer Infantry), Washington (1st Territorial V.I.), and Oregon (1st Oregon Volunteer Cavalry and 1st Oregon V.I.). These units mainly spent this time patrolling the overland emigrant routes, before being replaced by regulars at war's end.
Although a very interesting [well, at least to a native like me] historical overview, Converse's book is also maddening in that it's not footnoted for the benefit of those of us who would like to delve further. Also, the author's hand drawn maps are without scale, making the sites difficult to locate, even in general terms. As for what you can see today, the Whitman Mission and Massacre location is a very well-maintained (at least it was when I visited last) National Historic Site and the fort has a nice museum and cemetary, but I've never heard of markers placed at any of the sites of military action.
On a related note, I see Westholme will soon be releasing Fighting for Paradise: A Military History of the Pacific Northwest (May 2007). I might have to check that one out.