Henry Wallen attended the U.S. Military Academy from July 1, 1836, to July 1, 1840, when he was graduated and promoted in the Army to Bvt. Second Lieut., 3d Infantry, July 1, 1840.  Promoted to Second Lieut., 4th Artillery, on Oct. 4, 1840, Wallen served: in the Florida War, 1840-42; in garrison at Jefferson Barracks, Mo., 1842-44; on frontier duty at Natchitoches, La. (Camp Salubrity), 1844-45; and in Military Occupation of Texas, 1845-46.  In the War with Mexico he was engaged in the Battle of Palo Alto, May 8, 1846, where he was wounded, and the Battle of Resaca-de-la-Palma, May 9, 1846. He was promoted First Lieut., 4th Infantry, on Sep. 9, 1846.

After recruiting service during 1846-47; Wallen again was engaged in the War with Mexico during 1848.  After the war, he was posted on Commissary duty at East Pascagoula, Mis., 1848, and on frontier duty at Detroit, Mich, 1848-50.  From Feb. 1, 1849, to Jan. 31, 1850 he served as Adjutant, 4th Infantry, and was promoted to Captain, 4th Infantry, on Jan. 31, 1850.  

Wallen was in garrison at Plattsburg, N. Y. during 1850-52, as well as a time at Ft. Columbus, N.Y..  Heading west with his regiment, Wallen was on frontier duty at Benicia, Cal., 1852; Ft. Vancouver, Wash., 1852-53; Ft. Dalles, Or., 1853; Ft. Vancouver, Wash., 1853-55; Yakima Expedition, 1855; and Ft. Vancouver, Wash., 1856-57; on Recruiting service, 1858; on frontier duty at Ft. Cascades, Wash., 1858-59, He was in command of and exploring expedition to Salt Lake, Utah, 1859.  During 1859-60, he was back in Ft. Vancouver, Wash., and Ft. Cascades, Wash., 1860.

For a part of 1850, Wallen was in Washington, DC, on detached service 1860, but returned to frontier duty at Ft. Cascades, Wash., 1860-61.  He would join the 4th US in its journey back East at the start of the Civil War, moving through Camp Sumner, near San Francisco, and on detached service to the Isthmus of Panama.  Wallen was promoted Major, 7th Infantry, on Nov. 25, 1861.  During the Civil War, he served in operations in new Mexico from June 1862- June 1864, commanding a battalion and serving as Acting Asst. Inspector-General of the Department of New Mexico. From June 1864 - May 1865, Wallen was in command of a regiment at Ft. Schuyler, N.Y.

Wallen was granted a Brevet Lieut.-Colonel, and Bvt. Colonel on Feb. 23, 1865, for Meritorious Services Rendered by Him in New Mexico During the Rebellion and a Brevet Brig.-General, U. S. Army on Mar. 13, 1865, for Faithful and Meritorious Services During the Rebellion)

Wallen commanded the 1st Infantry at St. Augustine, Fla., May to Oct., 1865; and was in garrison at San Francisco, Cal., Dec. 15, 1865, to Jan., 1866; in command of the District of the Gila, Apr. 28 to June 10, 1866, and of the District of Arizona, June 10 to Aug. 11, 1866.  He was promoted to Lieut.-Colonel, 14th Infantry, on July 30, 1865

Wallen served: on sick leave of absence, Aug. 11 to Oct. 24, 1866; in waiting orders and on leave of absence, Oct. 24, 1866, to Mar. 1, 1867.  He took command of the Ft. Columbus Recruiting depot, N.Y., from Mar. 6, 1867, to May 5, 1869.  From May to Oct., 1869; he was assigned  on Special Duty at Headquarters of the Department of the East, Oct. 16, 1869, to Aug. 18, 1870.  Wallen was in command of 18th Infantry, headquarters Atlanta, Ga., Aug. 25 to Nov. 3, 1870; and served on duty at headquarters, Department of the East, from Nov., 1870, to Jan. 27, 1871, and with regiment, Feb. 3, 1871, to July 5, 1872; on Courts Martial, 1871-72; on Yellowstone Expedition, July 26 to Oct. 18, 1872, -- and at Omaha Barracks, Nebraska, to Nov. 20, 1872; on leave of absence to Dec. 23, 1872; commanding battalion of regiment to Mar. 2, 1873, during which time he was promoted to Colonel of the 2d Infantry on Feb. 19, 1873.  He commanded the 2nd US from Dec. 1, 1873, to Jan. 29, 1874.

He retired from active service on Feb. 18, 1871, for disability contracted in the Line of Duty.  Henry Wallen died on Dec. 2, 1886, at New York city, aged 68.