2 Answers

Some info on the 2nd Infantry here.

http://en.wikipedia.org/wiki/2nd_Infantry_Regiment_(United_States)

Following the reorganization the 9th Infantry performed garrison duty at various posts and guard duty on the Union Pacific Railroad line. In May 1873, six companies, A, D, E, F, H and I, were sent to the Department of Dakota for duty with the Yellowstone Expedition, escorting the engineers locating the Northern Pacific Railroad. From the summer of 1874 to May 1876, the regiment was stationed at posts on or near the Sioux reservation in Nebraska and Wyoming and was almost constantly escorting wagon trains. In the summer of 1875 Companies C, E and H, were in the Black Hills, Dakota, as part of the escort to the Newton–Jenney Party, Company E remained in the field until November assisting in ejecting white intruders who had entered Sioux territory.
In May 1876, Companies C, G and H became a part of the Big Horn and Yellowstone Expedition under command of Brigadier General Crook and were in the field until late in October taking part in the engagement with the Indians at Tongue River, Montana, 9 June, the Battle of the Rosebud, and the Battle of Slim Buttes. Companies G and H also assisted in repelling a night attack by Indians on the camp on Goose Creek, Wyoming, 9 July 1876. In the early part of September the entire command was without rations for a number of days, and subsisted on horse flesh and a small quantity of dried meat and fruit captured at Slim Buttes. In October, 1876, the Powder River Expedition was organized and Companies A, B, D, F, I and K formed a part of it. They remained in the field until January 1877, during the most severe part of the winter, and practically brought to a termination the Great Sioux War of 1876–77.
In July 1877, Companies B, D, F, H, I and K were a part of the force sent to Chicago, Illinois, at the time of the Great Railroad Strike of 1877. They remained a month performing guard duty over various public and private institutions.
During the summer and fall of 1878 Companies B, C, H and I were a part of a force of observation on the Little Missouri River, and in the northwestern part of the Black Hills.
In October 1878 Companies G and K were part of the force in the field in the Cheyenne War. Company K was mounted and took active part in the pursuit.
In October, 1879, Companies E and K went into the field in the White River War, remaining until July 1880.

http://en.wikipedia.org/wiki/9th_Infantry_Regiment_(United_States)