ST. HELENA. From the 1840s until the early 20th century, this grist mill was the center of social activity in Napa Valley, and settlers in the vicinity would gather to discuss pertinent events and oversee the grinding of wheat and corn. The mill's foundation was constructed entirely of native stone, and sturdy Douglas firs and redwoods were used in the walls and ceilings of both the mill and granary. Today, the mill and its 30-foot-plus waterwheel are protected by the state, as are a nearby pioneer cemetery and church, the first church built in Napa Valley.

SANTA ROSA. Luther Burbank, one of America's leading 19th-century horticulturists, lived in and worked on this parcel of land for many decades. On the property, he experimented with a few of the more than 800 varieties of plants that he developed over the course of his career. A contemporary of Thomas Edison and Henry Ford, Burbank often received both men as guests at his downtown home. Today, the acre of gardens features a cutting garden, medicinal plants, roses, and more. The greenhouse, constructed in 1889, features rotating exhibits and a replica of Burbank's office; the carriage house, renovated as a museum, preserves a variety of Burbank's personal effects. It also boasts a gift shop.