The Union has made some physical changes over the years. Originally located at the corner of Mill and Main streets in Grass Valley, the facility was moved in 1906 to 151 Mill Street.That building accommodated a then-modern, but noisy, duplex press. In addition to printing The Union, the Mill Street location provided job printing facilities of all kinds.The newspaper's last move was in 1978 from the downtown Grass Valley address to its current facilities in the Glenbrook Basin on Sutton Way.The printing press was also updated to a nine-unit, offset installation which features high-speed printing and precision color and black-and-white …