As the Gold Rush drew miners to the Sierra Nevada, Stockton grew into a major logistical and mercantile hub for the San Joaquin Valley and Mother Lode, which allowed for the City and County populations to rise significantly between 1850 and 1870. As the state's gold economy waned in the 1870s, San Joaquin County transitioned into a major national center of agriculture, which it remains to this day. Reclamation of the California delta, which began in 1869, strongly benefited this agricultural growth. The importance of agriculture to the region's economy led to the creation of a dynamic industrial engineering sector in Stockton, Lodi, and nearby Rio Vista in the 1880s. Notably, the Sperry Flour Company, Holt Manufacturing Company, the operation of R. G. LeTourneau, Samson Ironworks, and the canning empire of Tillie Lewis were firms of national and international significance. Holt Manufacturing, led by Benjamin Holt, would pioneer the industrial manufacturing and sales of the tractor, while R.G. LeTourneau patented the bulldozer in 1926.