Hello!!!!
I just saw this post in 2012. I hope you're still on ancestry and looking.

I don't have photos and I don't have a grave site, but Alexander is part of my family too. I have been tracing the McCormicks since I've been about 12 years old. My gg grandfather, Robert, is Alexander's younger brother. Here's what I have on A G McCormick.

I do own a pair of mounted bull horns that came from his ranch around the turn of the century.

Ellen McCormick Gerwitz
egerwitz@frontier.com

M05) Alexander George (27 MAY 1833 Charlottenberg, Glengarry, Ontario, CAN d. 10 JAN 1911 Liberty, Liberty, TX) married (@1867) Catherine B. McManus (b. 1841 Texas d. 08 MAY 1902 Liberty, Texas) They had at least one child:

(M05a) Lula (b. 1870 Texas d. after 1880)

Notes:
1861 -1865: CIVIL WAR - CS - Living in TX at start of war, was forced to muster in and served for throughout the war
Martin's Cavalry (Fifth Partisan Rangers) /5th Cavalry (Martin's 5th Mounted Volunteers; 2nd Regiment, Sibley's Brigade)
McCormic A. G. Sergeant Co. A

1870 Census: Chambers Texas: George McCormack b. 1833 Canada; Catherine b. 1843 Texas)

1875 Chambers Co, TX - Cattle Brands and Ear Marks - McCORMACK, A. G., 63, 191

1880 Census: Libery, TX: A I. McCormic b. 1833 CAN, Farmer / C. B McCormick b. 1841 TX/ Lula (b. 1870 TX - daughter), D. B. Tevis (b. 1872 TX farmhand)

1900 Census: Liberty, TX: George McCormick - b.May 1833 CAN, Catherine McCormick (b. Dec 1839 TX) , Catheline McCormel - niece (b. Nov 1890 TX)
Catherine's mother was born in MS and her father in NY.

1910 Census: Liberty, TX: A.G. McCormick b. 1833 CAN, listed as widowed - immigrated 1858; W L Douglass M 56y, A G Mccormick M 77y , Sam Cameron M 38y, Frank Wilkerson M 32y. Lucy Antwine F 20y

Probates - Liberty Co, TX
McCormick, A.G., deceased (no papers) filed Jan. 17,1911 492
McCormick, Catherine B., deceased filed Aug. 10,1902 344