Without actually having to travel all the way up the Clearfield, I’ve been looking for a date that would show when the factory was built. It looks like I’ve come pretty close with this letter, which is titled “Article of Agreeement”. Here we see that on August 11, 1920, the plot of ground on which the “buildings now occupy” is the property of J.E. Gearhart. And also, the buildings and machinery which occupy said plot belong to the Gearhart Knitting Machine Company. According to this letter, the Gearhart Knitting Machine Company was also incorporated on this date.
Assuming that it took at least a year to build the factory, I’d say that construction started around the 1918 or 1919 time frame, just after World War One, and was completed by August 11, 1920. Even today, it is a pretty impressive structure for a small town, expecially since the surrounding area has remained mostly residential. The tree-lined factory stands out among the houses and tree-lined streets.