Grantsville, the county seat of Calhoun County, is situated in a bend of the Little Kanawha River at the intersection of State Routes 5 and 16. Laid out in 1866 and named for Ulysses S. Grant in 1867, Grantsville was incorporated in 1896. It remains the only incorporated town in Calhoun County.

The courthouse, on the square in the center of town, was completed during World War II and is the fourth to occupy the site. The exterior is made of Arnoldsburg Formation sandstone, quarried locally. Grantsville has several other structures built from this same quality stone.

Grantsville benefited from the timber and oil and gas booms that began in the late 1800s. Consolidated Natural Gas, now Dominion Hope, has maintained a district headquarters in Grantsville since the 1920s. In the early 20th century, Godfrey L. Cabot operated the world's largest carbon black factory two miles outside town, using natural gas as a raw material. More than 50 shallow-draft gasoline-powered sternwheelers were constructed in and around Grantsville for use on the Little Kanawha River.

The county's only print newspaper, the Calhoun Chronicle, has been published in Grantsville since 1883. The Minnie Hamilton Health System, constructed on a hill overlooking the town in the 1950s as Calhoun General Hospital, now serves the citizens of Calhoun and surrounding counties. The Calhoun County Public Library is located in Grantsville, as is a town park featuring a swimming pool, picnic shelters, tennis and basketball courts, and a playground. Grantsville's modern water system supplies customers as far north as Ritchie County and south to Arnoldsburg. Calhoun Banks, headquartered in Grantsville, has branches in Arnoldsburg, Elizabeth, and Glenville.

Regular flooding, two disastrous downtown fires, and the relocation of Route 16 have changed the appearance of the town and destroyed many original buildings. Grantsville's 2020 population was 482, about half of what it was in the mid-1900s. In addition to Godfrey L. Cabot, other prominent residents have included antiquarian Boyd B. Stutler, Congressmen John M. Wolverton and Robert H. Mollohan, and West Virginia First Lady Hovah Hall Underwood.