Agriculture in the United States has undergone a radical transformation in the last 100 years. The number of farms has declined from 6 million to around 2 million. The average size farm has increased from around 150 acres to 400 on average. This transformation has allowed greater farming efficiencies. But, there are also significant downsides, including: soil exhaustion, groundwater contamination, the decline of family farms, and the decline in the working conditions of farm laborers.
Source: UC Davis - Sustainable Agriculture Research and Education Program