About 1840, German immigrants in Texas and throughout the United States had begun expressing their preference for lager beer, which was brewed with a bottom-fermenting yeast that used secondary fermentation. It had to be aged at a cool temperature for four weeks to nine months. The majority of the Texas breweries built during this period brewed only lager beer. Since there was little artificial refrigeration or mechanization in Texas before 1860, almost all beer was brewed in the cool months. It was usually stored in some form of cool cellar until the aging was completed.