Ernest was the son of Privy Counselor Johann Hermann (1795 – 1871) & Laura (Antonie de Greiff) (1798 - 1845) Altgelt. Both were born & died in Germany.

His siblings were: August Hermann, Friederike Antonie, Laura Elisabeth Antonie, Therese Antonie, Anton Hermann, & Bertha Auguste.

The story of Ernst is a fascinating one. This is a summary of his life from various historical sources.

Ernest was born at Düsseldorf, Nordrhein-Westfalen, Germany on July 17, 1832, the son of a privy counselor of that city. Upon completing military service, he immigrated to New Orleans in 1851 when he was 19 years old & worked for the cotton firm of John Vles for a short time.

In 1854, when he was 22, he led a surveying party into the Hill Country of Texas & laid out the town of Comfort on property owned by Vles & is credited with surveying and measuring lots that were later sold to German immigrants.

Ernst met Emma Franziska Murck in New Braunfels in 1855, where she was living with relatives. He was so eager to woo her that he joined the Sangerfest singing group from Sisterdale, as a tenor, traveling to the concert via a team of oxen.

Emma, an aspiring journalist, later wrote about her early days in "Beobachtungen und Erinnerungen" which ran in Guido Ransleben's book, "100 Years of Comfort":

Emma wrote "It so happened that one of the men who attended the Sangerfest in New Braunfels and who found lodging in her friend's home, was Ernest Altgelt. Returning from a ride through beautiful Landa's Park with this dashing cavalier we announced our engagement to my mother and friends, and six weeks later we were married in San Antonio. After several days' sojourn we returned to New Braunfels from where we started on our eventful trip over rocky paths by way of Sisterdale to the new settlement of Comfort. Thus I abandoned all ambitions I may have had in the field of journalism, to embark on what was to become the greatest career of all - the mother of the children of the man who would carve a garden spot in the wilderness providing comfort for those who had the determination of self-expression and self-preservation."

Ernst married Emma in San Antonio on July 23, 1855, after which he took up the practice of law. They had nine children in the township of Comfort: Antonia Laura, Hermann Hugo, George Conrad John, Helene Eveline, Ida Adele, August Ernest, Wilhelm Otto (1868 – 1873), Franz Hugo (1869 – 1878), & Ernest Junior. Wilhelm & Franz died before Ernest.

During the Civil War, some residents of the area favored secession from the North. However, many Germans voted to remain loyal, and Ernst offered his help. Some of the avowed Loyalists had to remain in hiding until they felt it safe to get into Mexico to avoid either imprisonment, the bearing of arms on the Confederate side, or possible execution. Ernst let it be known to those who kept themselves secreted that the latch on his smoke-house was always open.

Ernst's health was fragile by then, and he returned to Germany to visit his father, but the "disturbance" raged longer than he had estimated. Meanwhile, Emma managed to run things on her own. After his return, the family relocated to San Antonio in 1866, where he practiced law.

He moved to San Antonio with his family in 1866, continued his practice of law, & increased his real estate investments. Some claim that he built the first house on King William Street in 1867, and was given the honor naming the street, allegedly after Wilhelm I of Prussia. His neighborhood rapidly attracted successful families of German and other nationalities. Altgelt built a more elaborate second home in 1877–78 at 226 King William Street.

Ernst died from a heart related illness on March 28, 1878, and was buried in the family cemetery at his Wasserman ranch retreat (about twenty-five miles from San Antonio).