There are more hazardous waste sites in New Jersey than anywhere else in the United States.
In 1998, The Garden State had 109 hazardous waste sites on the national priorities list for the federal Superfund program or 8.7% of the national total. The state's land area is just 0.2% of the United States. New Jersey's hazardous waste density (the number of sites per 1,000 square miles) was 14.7 or 40 times the national average. (Source: A Geography of New Jersey: The City in the Garden by Charles A. Stansfield)
I could see New Mexico and Nevada because of all the Nuclear research and weapons development that happens there. But why New Jersey?
Of course when I think of Hazmat. I think Nuclear & Chemical mostly. But even Gas stations are considered Hazardous sites because of fuel leakage.