Write a question about the following article: On 17 April 1875, regimental headquarters for the 9th and 10th Cavalries were transferred to Fort Concho, Texas. Companies actually arrived at Fort Concho in May 1873. At various times from 1873 through 1885, Fort Concho housed 9th Cavalry companies A-F, K, and M, 10th Cavalry companies A, D-G, I, L, and M, 24th Infantry companies D-G, and K, and 25th Infantry companies G and K. The 10th Regimental's mission in Texas was to protect mail and travel routes, control Indian movements, provide protection from Mexican revolutionaries and outlaws, and to gain knowledge of the area's terrain. The regiment proved highly successful in completing their mission. The 10th scouted 34,420 miles of uncharted terrain, opened more than 300 miles of new roads, and laid over 200 miles of telegraph lines.

Question about the article:
How many cavalries were transferred to Fort Concho on 17 April 1875?