The Origin of the Alma Mater
From the April 1942 Assembly magazine:

From the 1947 Bugle Notes:
"Alma Mater," most beloved of all West Point songs, had its beginning in a very inauspicious manner. In the fall of 1908 Colonel, then Cadet, Reinecke was walking the area as a result of a bit of frivolity in Yearling Camp the preceding summer. Attempting to pass some time he tried to compose a furlough song. (It was the custom at that time for Yearlings to congregate at Battle Monument to "bay at the moon" and to sing furlough songs.) Finally he began to tramp to the tune of "Treueliebe," an old favorite composed by Kuecken in 1827. Gradually he developed the words to what we know today as the "Alma Mater." The song, however, died the death of all furlough songs and was not even sung at the graduation of Reinecke's class in 1911. On June 9, 1912, one year after Reinecke's graduation, "Alma Mater" was sung at the Baccalaureate Service and took its place as a musical expression of the feelings of every West Pointer toward his Alma Mater.

From the liner notes of the West Point Music record album (courtesy Lew Higinbotham '62):
For a display of youthful ebullience that had no place in the ordered schedule of the USMA, Cadet Paul S. Reinecke, Class of 1911, was pensively walking the Area one day in the fall of 1909 when the idea for this song suddenly came to him. To the old German tune of "Treueliebe", line by line and verse by verse the structure of "Alma Mater" was developed to the rhythm of his measured pacings. The words struck a responsive chord in the Corps and "Alma Mater" achieved instant popularity.

From a Lieder web site (courtesy Wolf-Ekkehard Hindrichs USMA 2008):
The melody may have been written by Georg Heinrich Lux or Friedrich Silcher, 1827