James was refused for active service on account of health and served in the home guard in Lynchburg.

[3][4] On September 11, 1865 after the conclusion of the Civil War, Alpha Tau Omega was founded by the three founders, Otis Alan Glazebrook, Alfred Marshall and Erskin Mayo Ross.

In the Fall of that same year, the returning cadets were temporarily lodged in private residences and the hotels of Lexington, Virginia.

Of him, former national ΑΤΩ president Joseph R. Anderson said, "During the years he was the head of the great institution in Texas he was recognized far and near as a Christian scholar as well as a wise administrator and a most useful citizen.

Once again, he joined his friend and fraternity brother, John Garland James who was serving as the college's 2nd president of Texas A&M.

Dinwiddie passed away on December 11, 1887, in Austin, Texas, and was buried in Oakwood Cemetery (Section 1, Lot 67).

According to an article in the Austin American-Statesman, Dinwiddie died of pneumonia which was "contracted during the summer among the mountains in Colorado".

He needs no other.That, in his death, the college has suffered an irreparable loss, and the state a deplorable calamity because he devoted every energy of his heroic nature to the task of establishing this institution upon a foundation of enduring prosperity, and because he was the advocate and the champion of educational progress.

That the cause of education has lost a shining light, and we, a leader, associate, and friend, whose image will abide in our hearts always; whose example will inspire and encourage us, and be treasured by our successors for all time to come.The Texas A&M Corps of Cadets also published resolutions of respect to the Austin American-Statesman.

The cadets wore mourning attire for thirty days in Dinwiddie's honor after his death and also submitted the following statement:[13] That in the death of Major H. H. Dinwiddie this college loses an earnest worker, who was always active and zealous in the performance of his duties; ever ready to advance tne interest of this institution; devoted to its welfare and prosperity; one who was wise in counsel and fearless in action, an honest and upright man, whose virtues endeared him not only to his students, but to all his fellow citizens.In 1889, two years after Dinwiddie's death, the construction of the Assembly Hall[14] began on the A&M campus.

In tribute to Dinwiddie, a large marble tablet commemorating him was installed in the wall of the building directly behind the pulpit.

[16]No longer does the quiet, dignified form of a Dinwiddie grace the president's chair or mansion, but he lives in the heart of every co-laborer who survives him, in the heart and life of every student who knew him, in every hand that that received his kindly grasp – yea, he lives in the dignity and classic stability he gave to our college.

And as long as the A. and M. shall live and her alumni breathe the free air of Texas, the name H. H. Dinwiddie will live and inspire them to higher and nobler deeds... A Dinwiddie to establish and dignify the institution — a Ross to uphold and popularize it — and a Foster to expand it into the saving hope and glory of the Empire State of Texas.