Glass blower William John Blenko built his first factory in Milton in 1921. Born in England on December 8, 1854, Blenko was determined to introduce antique stained glass production into his adopted country. Prior to his arrival in West Virginia, he made several failed attempts to establish his business. Blenko came to the U.S. in the 1890s, settling first in Kokomo, Indiana. While there, he became lifelong friends with Socialist leader Eugene V. Debs. Due to economic circumstances, Blenko was forced to return to England to continue his craft. In 1899, he returned to America and tried to set up shop in Point Marion, Pennsylvania. That effort failed, as did a later attempt in Clarksburg.

His first Milton plant, described as a shack by those who remember it, was known as the Eureka Art Glass Company. Blenko slept in a corner and lived on $3 a week. In 1923, he was joined by his son, William H., and daughter-in-law, Marian. His son was an able glassmaker and an even better salesman. Orders for the stained glass began to come in from the U.S. and Europe. The Great Depression however, nearly proved fatal to the business.

By 1930, William H. Blenko became convinced that diversification was the key to survival. The company began producing the decorative glassware for which it is most famous today. While stained glass production continued, the demand for decorative ware grew steadily. By the mid-1940s, Blenko glass was famous, having been featured in such publications as Time, National Geographic, House Beautiful, and House and Garden. Blenko stained glass can be found in the National Cathedral in Washington, the Cathedral of Rheims in France, the chapel of the U.S. Air Force Academy in Colorado, and many other places. Blenko also manufactures the prize for the annual Country Music Awards.

William John Blenko worked until his death in 1933 at the age of 78. William H. Blenko led the company until his death in 1969. He was succeeded by his son, William H. Blenko Jr., now chairman of the board. Walter Blenko Jr., another grandson of William John Blenko, was president until his death in 2019.

Like other West Virginia glass companies, Blenko struggled financially, leading to a bankruptcy filing in 2011. Renewed interest in the company’s products and lower gas prices have helped the company recover since then. In 2022 Blenko partnered with the U.S Department of Labor Apprenticeship Program and the West Virginia Department of Economic Development to create the state's first registered Glass Worker Apprenticeship program.

Blenko Glass is open regularly to the public, featuring glass-blowing demonstrations and a showcase of products.