He was examined and given a certificate to practice by M. S. Crow, M.D., chairman of the board of medical examiners, Erath County, Texas, and this was recorded on the twenty-seventh of November, 1878, at the office in Stephenville by W. H. Fooshea. His health grew worse, and he was advised to make a trip to the Gulf. In a covered wagon, with his brother Ritchie as driver and with his wife and two children riding nearby in a buggy, he set out from Duffau on May 15, 1881. Because he grew worse daily, all were compelled to return within a week. Before he turned back, he stayed for a short while at the home of a friend in what is now downtown Austin. The historical site is presently part of 6th street's bar district. While the upstairs loft where Letterman spent his last days has held many merchants during the last century, it is currently a bar named Peckerheads. A small shrine in Letterman's honor exists there today. He died on May 23, 1881, and was buried in the cemetery at Duffau. The Revered Mrs. Hugart conducted services at the church, and Mr. Franks conducted the Masonic service. Letterman sold a riding pony, which her husband had given her, and had a monument placed at his grave. This monument still stands. Shortly after Dr. Letterman’s death, his widow and children returned to the home of Mrs. Letterman’s father, Professor Slaughter, in Missouri. The last lines Dr. Letterman wrote were these:  "Dear Sir (Prof. Slaughter)"  "Today I am used up right sharp—does not express my case too strong. At all events after careful advice, I leave tomorrow, closing the housing and go direct to the Gulf at the mouth of Rio Grande del Norte. This is 400 miles from here. We go through Lampas, thence to Austin, then to the mouth of River, then we rest for 2 or 3 weeks rolling in salt water, then we make a bee line for San Antonio, Laredo, and return home if well. If not well, keep agoing. I will close. Your next, if this is answered, you will direct to Austin. Good-by." "Love to all,"  "W. H. Letterman"