Thompson's Island Homeplace

The dam outlived the mill. John Matthew Cape's family later ran a gin on the waterpower just above the islands, with a turbine of about 125 horsepower. The city took possession of the dam and island in January 2013, and the 2015 floods damaged it. In March 2016 the council voted for removal. The Texas Historical Commission argued for keeping the dam, and the federal wildlife service said it would withdraw if any part remained. Opponents of the marker date the dam to 1869, and a 2020 challenge led to new research by historian Joleene Snider.

What the plaque says

Thompson's Island Homeplace Dr. William Alexander Thompson (1803-1879) made an agreement with neighbors in 1850 to use the San Marcos River for irrigation and as a source of energy. He and his sons William A. and James used slave labor to build a gristmill, sawmill and cotton gin. The land masses formed by digging a ditch for the waterwheel and a sluiceway from the river were called "Thompson Islands." The Thompsons directed the business until 1911 when John Matthew Cape (1861-1933) bought the mill. The use of electricity in 1942 ended the mill's need for water power. (1979)

Where it stands

Worth the stop nearby

• Spring Lake and the Meadows Center — 1.5 mi
  The headsprings of the San Marcos River, among the longest-inhabited places in North America, once an amusement park with a swimming pig and now seen from glass-bottom boats.
• Gruene Historic District — 14 mi
  A cotton town on the Guadalupe that the boll weevil emptied, rescued in the 1970s by a kayaking architecture student, with a dance hall that says it has never closed.
• Lockhart Courthouse Square — 15 mi
  A cotton-era courthouse town named the Barbecue Capital of Texas, built near the 1840 Plum Creek fight that followed the killing of Comanche leaders at peace talks.
• Sophienburg Museum and Archives — 17 mi
  The hilltop where Prince Carl of Solms-Braunfels raised the Adelsverein's headquarters in 1845, now the museum and archive of the German colony that became New Braunfels.

More markers nearby

• Thompson's Islands — steps away
• La Sociedad Mutualista Cuauhtémoc — 0.8 mi
• Wesley Chapel A. M. E. Church — 1.0 mi
• First National Bank of San Marcos — 1.1 mi