The bridge locals call the San Marcos Bridge, or the Thompson Island Bridge, crosses the San Marcos River near Cape Street and East Guadalupe, close to Sewell Park. It is a low concrete span. Teenagers jump from it in the daytime. The ghost story attached to it is a Confederate soldier who is said to walk the bank when the country is at war. There is no name for him, and no death record that places a soldier dying at that crossing.
The islands themselves are documented. In 1850 Dr. William Alexander Thompson, who had come from Louisiana, made an agreement with neighboring landowners to use the San Marcos River for irrigation and power. He and his sons William A. and James used enslaved labor to dig a millrace and a wasteway by hand. The ditch cut three land masses out of the channel. Those became Thompson’s Islands. The mill that went up on the site ran a gristmill, a sawmill, a shingle machine, and a cotton gin. A Texas Historical Commission marker at Conway Drive and River Road, placed in 1979, states the slave labor plainly. The Thompsons ran the works until 1911, when John Matthew Cape bought them. Electricity ended the need for the waterwheel in 1942. The millrace, the dam, and the islands are still there. That is the documented history. The soldier is not in it.
The legend, as it appears in Brian Righi’s Supernatural Texas and in local retellings, says Confederate sentries were stationed at the bridge during the Civil War. Drivers crossing at night, when fog comes up off the river, are said to see them pacing, in gray and yellow uniforms, with caps and capes, holding Kentucky long rifles at attention. The most common version is a single soldier who lived in a cabin at the far end of the bridge. He and his brother made a pact before they left for the war: they would come home, no matter what. He did not. He is said to still be trying to keep the promise, and to show himself more often when the country is at war. No contemporary account names him, places him at that post, or records his death there. Hays County sent men to the Confederate army in 1861. That is the only documented military fact attached to the county in that year.
A second story is modern. A businessman came to look at Thompson Island for a restaurant. Crossing the bridge he felt cold spots. On the island he heard low growling and the sense of being watched. Walking back, he turned and saw a human-shaped shadow in the bushes. He left. That night he dreamed the river was on fire and the figure was still there. No restaurant was built. Locals call the figure the Nightmare Man. It does not appear in the older tellings.
What is documented is a millrace dug by enslaved workers in 1850, a cotton gin and sawmill that ran for ninety years, and a bridge that now carries the name of the islands the ditch created. The soldier in the gray and yellow uniform, and the man in the bushes, are the stories the town tells. There is no body and no name behind either of them.
The Thompson’s Islands historical marker and the millrace channel.
Relevant links
San Marcos Record: the library’s legends file — the Righi account of the sentries
San Marcos CVB: Spooky San Marcos Stories — the soldier and the Nightmare Man
Haunted Places: Thompson Island Bridge — the brother-pact version
KTSW: Haunted Locations, Thompson Island Bridge — the 1850 mill and the slave-labor marker
Thompson’s Island Homeplace marker — the 1979 Texas Historical Commission text