In 1907, John H. Mittendorf began construction of what became known as the Rock House (aka Boulder House), his private retreat in the hills of southeastern Indiana. Built from more than a million stones gathered from 48 states and several foreign countries, the home quickly became a local legend. According to tradition, John personally laid every stone and mixed every batch of mortar by hand. With help from local farmers, he hauled much of the material from the nearby rail line to the property. Children from the area frequently stopped to watch the construction and he became known for handing out candy to visitors.

John was born in Dayton, Ohio, in 1865, the son of Rev. William Mittendorf, a German immigrant and minister in the Church of the Brethren. After a brief career as a preacher, Rev. Mittendorf became editor of two German-language church publications and managed the denomination's printing operation. John and his brothers spent much of their youth working in the family print shop, but by his early twenties, John decided he did not want to spend his life in the printing trade.

In the mid-1880s, he joined the Croft&Allen Company as a traveling salesman. The Philadelphia-based company produced cocoa, chocolates, Nadja caramels, chewing gum, and some of the earliest candy-issued baseball cards. At a time when baseball cards were still a novelty, the backs often featured advertisements instead of player statistics. John traveled extensively throughout the Midwest selling the company's products and became so respected in the trade that he earned the nickname "Dean of Confectionery Salesmen."

While working for Croft&Allen, John married Rosa Tieman and eventually settled in Cincinnati. The couple never had children. During his years on the road, he developed the idea for "Coin Gum", a chewing gum wrapped in foil and stamped to resemble coins. Before launching the product, he took a world tour and collected foreign coins to distribute as promotional keepsakes to candy wholesalers and retailers. While traveling through Switzerland, he became fascinated by the stone homes of the Alps—an inspiration that would later shape his most famous project.

Rosa never shared her husband's enthusiasm for the remote stone retreat and reportedly visited only rarely, if at all. Meanwhile, John continued expanding and refining the property. When Highway 52 was later constructed nearby, he even altered the orientation of the house so that its front entrance faced the new roadway.

After retiring from Croft&Allen in 1915, John devoted himself fully to completing the Rock House. He lived there for many years until Rosa's death in 1930. Following her passing, he lived for a time with a nurse before retiring to Fort Myers, Florida, to stay with one of his brothers. John Mittendorf died there in 1940 and was buried beside his wife at Spring Grove Cemetery.