According to the 2010 EPA Municipal Waste Facts and Figures Fact Sheet:
In 1970, 350 thousand tons of disposable diapers went to landfills
In 2010, 3,740,000 tons went to landfills
The 2010 number is actually down from 3.8 million tons in 2009 but that's still a staggering number. Here's hoping 2011's number will be even lower!