When a mysterious fire destroyed his dugout, however, George Nickel's post office never opened.

In 1902, the Chicago, Rock Island and Gulf Railway set up a station in the town, calling it "Wheeler" like the county, but later changing it back to the original name of Shamrock in 1903, which prompted the reopening of the Shamrock post office.

[6] The town continued its growth as other businesses moved into the city, including the county newspaper, which moved from Story and renamed itself from the Wheeler County Texan to the Shamrock Texan, several banks, and Shamrock Cotton Oil Mill.

A decline in the oil industry caused the population to drop in the 1940s, but it rebounded in the next decade with the improvement of Route 66.

According to the 2020 census, the city population has dropped to its second lowest recorded point with 1,789 residents.

According to the United States Census Bureau, the city has a total area of 2.1 square miles (5.4 km2), all land.

[13] At the time of opening, the U-Drop was the only café within 100 miles (160 km) of Shamrock, enjoying brisk business and becoming a successful establishment.

[15][19] With a $1.7 million federal grant, the city was able to hire a firm specializing in historical renovation to restore the building to its original condition and adapt it into a museum, visitors' center, gift shop, and the city's chamber of commerce.

[15][20][21] The revived U-Drop Inn was featured in the 2006 animated film Cars as the inspiration for the fictional Ramone's body shop.

[22] The Old Reynolds Hotel, a historic building, was saved from demolition and converted into a museum by local residents.

The building with 25 rooms was turned into an exhibition hall with pioneer artifacts, typical objects of settlers, and Native American arrowheads.

Irish Craftfest is held annually the first weekend of October at the Shamrock Area Community Center.