Individual Details

Although reported to be a twin to Orrin, I have found no proof.

On Google Books:
Hobart College, General Catalogue 1825-1897.
"Graduates and Students"
1829, p.32
Nathaniel Orin Allen. Son of Nathaniel. Richmond (Allen'sHill). Union '29. M.D., Physician, Va.
1833, p.37
Students at Hobart College, west of Albany, State of New York
Augustus Porter Allen, Bro. of Nath. O., '29. Richmond. A.P.D.

Congressional Serial Set
Historical Register and Dictionary of the United States Army, from its Organization, September 29, 1789, to March 2, 1903. By Francis B. Heitman. Washington. Goverment Printing Office. 1903.
Part II. Alphabetical List of all Commioned Officers of the Army....
p.157
Allen, Augustus Porter, N.Y. Cadet M.A. 1 July 1832; 2 lt 3 art, 1 Jul 1836; 1 lt 23 Nov 1837; 1 lt topl engs, 7 Jul 1838; died 1 Sep 1841

General Scott, by Marcus Joseph Wright, 1893 [also on Google Books]
Note: Winfield Scott (13 Jun 1786 - 29 May 1866) military commander. During the 1830's Scott negotiated an end to the Black Hawk War, took part in the Second Seminole War & the Creek War of 1836, and presided over the removal of the Cherokees. President Andrew Jackson ordered him to Illinois to take command of the Black Hawk War, 1832. The 2nd Seminole War broke out in Dec of 1835 and Scott arrived in Florida by Feb of 1836.
Chapter V in the book deals with that war. Council held 23 Oct 1834. The Indians would be required to move 1835-37 - the Seminoles were to settle among the Creeks, west of the Mississippi. They did not want to go. In another council, 22 Apr 1835, President Jackson sent a letter telling them must go. The entire military force in Florida was 489 officers and men - the Seminoles were in the peninsula in the swamps and creeks - Osceola, their leader.
p.99 Steamers with volunteers arrived from New Orleas at Hillsboro Bay, four miles from the garrison, Feb 8, 9, & 10th (1836). At the fort were about 200 regular troops, composed of Companies A, B, C, and H of the 2nd Artillery and Company A of the 4th Infantry with Majors Francis S. Belton, Richard Augustus Zantzinger & John Mountford; Lieutenants John Breckenridge Grayson, Samuel McKenzie, John Charles Casey, Thomas C. Legate, Edward Wright Morgan, Augustus Porter Allen, and Benjamin Alvord, and Surgeons Henry Lee Heiskell & Reynolds. Major Belton was the commanding officer of the post.

Letter found on Fold3
Allens Hill July 27th 1836
Hon. Lew. Cass
Secty of War
Sir
The appointment of 2nd Lieut in the 3rd Regt of Artillery which the President of the United States. (by and with the advice & consent of the Senate) has been pleased to confer on me is hereby accepted.
Very Respectfully
Your Obdt Servt
A. P. Allen
2nd Lt, 3rd Arty.
Note: I was born in the State of New York
Certificate of the Appointment dated 27 Jul 1836

Ontario Co DB 73, p.125
27 Aug 1840 Augustus P. Allen and Robert L. Rose, Executor of N. O. Allen of Richmond, to George Geiger of Lima, Livingston Co. In consideration of $1 convey all that tract of 156 rods out of the SW corner of lot number 4, township 9, 5th range [which would be Richmond] ....along the centre of the highway; 156 rods includes highways. Signed: A. P. Allen, Executor Robt. L. Rose, Executor.
7 Oct 1840 Robert L. Rose acknowledged the deed to Harry Smith, Commissioner of Deeds. Recorded 28 Nov 1842.

Named in the will of his brother Nathaniel O. Allen in 1839. Deceased by 1849 when the Executor and brother-in-law Robert L. Rose stated that Orrin N. Allen of Culpeper Co was now the only heir at law.

Birth	20 Apr 1812
Death	1 Sep 1841

Father	Nathaniel Allen (1780 - 1832)
Mother	Almyra Akin ( - 1814)
Sibling	Almira Allen (1803 - 1849)
Sibling	Almiron W. Allen (1805 - 1829)
Sibling	Nathaniel Orin Allen (1810 - 1839)
Sibling	Orin Nathaniel Allen (1812 - 1875)