Most of the Lodi sub-appellations are growing regions almost exclusively and have only a few, if any wineries. The Mokelumne River AVA is the exception. It contains almost 90 wineries as well as the vineyards to support them.
The name of the region comes from the river that forms the boundary and flows through the area. Mokelumne means people of the fishnet in the Miwok language and has been cited on maps of California since John C. Fremont marked it in 1848.
The boundaries of this appellation are defined by the young alluvial fans of the Lower Mokelumne as well as the creeks and sloughs that feed into the river. The soils are fine, sandy loams of the Tokay and Acampo series. These soils are young and deep (6-12 feet) with good drainage and a low ability to hold moisture.
The elevation is the lowest in the region, being only five feet above sea level in the southwest corner. This allows cool Pacific air to move up through the Golden Gate to the Carquinez Strait into the Sacramento-San Joaquin Delta and finally into the Mokelumne River. The constant inundation of cool air makes this appellation the coolest in the area and increases the degree days required to grow vinifera grapes from 50 to 450. The extra time required to harvest the fruit gives the grapes more time to develop richer flavors.
This cool air is prevent from forming frost on the vineyards by the winds moving down from the Sierra Nevada Mountains to the east. These winds keep the air circulating instead of forming ice crystals.
This area of the Lodi region has been producing wine grapes since the 1880 when George West started a vineyard near the southern border of the appellation. The most common grapes in the 19th century were Zinfandel and Flame Tokay whose’s vines would grow old in the poor soils searching for water and nutrients. In other regions the designation of “old vine” might be given to plants of 30 years. In the Mokelumne River area, the vines might be over 100 years old.
Being the largest of the of Lodi sub-appellations, Mokelumne River is also home to the lions share of the wineries.