GUN BARREL CITY — For more than eight decades, Jim Howell was hardly one to cause a political ruckus. But this spring, he realized that a crude-oil superhighway ran through his backyard, just two feet below his patchy lawn and seven feet beyond a newly built porch.

“At first I felt guilty and stupid,” Mr. Howell said about discovering that the 20-inch-wide pipeline passed so close to his compact brick house.

Guilt became alarm as he read more about it and as people from ExxonMobil, its operator, showed up to add a row of yellow-and-black- striped warning markers. The pipeline, Pegasus, was the same one that ruptured about 280 miles northeast in March, spewing at least 210,000 gallons of heavy Canadian crude into neighborhood streets in Mayflower, Ark.

Now, at 83, Mr. Howell admits to having become an activist, even if he is not particularly fond of the label. Loosely organized by two local citizens’ action groups, Mr. Howell and others in this small Henderson County town — whose official motto is “We Shoot Straight With You” — make up a small but growing pocket of East Texans who are asking federal regulators to shut down the pipeline permanently. The 65-year-old pipeline, which runs from Patoka, Ill., to Nederland, Tex., has been turned off since the spill while ExxonMobil complies with a corrective-action order from the United States Pipeline and Hazardous Materials Safety Administration.