Here is a list of the top 10 worst oil spills in the whole world.
These ten oil spills, all massively larger than the Exxon Valdez, were all smaller new stories, either because the ships were offshore, or dropped their toxic loads in less developed parts of the world. The Valdez spilled 10 million gallons off the coast of Alaska, the smallest spill in the top ten was four times larger.
1. Kuwait - 1991 - 520 million gallons
Iraqi forces opened the valves of several oil tankers in order to slow the invasion of American troops. The oil slick was four inches thick and covered 4000 square miles of ocean.
2. Mexico - 1980 - 100 million gallons
An accident in an oil well caused an explosion which then caused the well to collapse. The well remained open, spilling 30,000 gallons a day into the ocean for a full year.
3. Trinidad and Tobago - 1979 - 90 million
During a tropical storm off the coast of Trinidad and Tobago, a Greek oil tanker collided with another ship, and lost nearly its entire cargo.
4. Russia - 1994 - 84 million gallons
A broken pipeline in Russia leaked for eight months before it was noticed and repaired.
5. Persian Gulf - 1983 - 80 million gallons
A tanker collided with a drilling platform which, eventually, collapsed into the sea. The well continued to spill oil into the ocean for seven months before it was repaired.
6. South Africa - 1983 - 79 million gallons
A tanker caught fire and was abandoned before sinking 25 miles off the coast of Saldanha Bay.
7. France - 1978 - 69 million gallons
A tanker's rudder was broken in a severe storm, despite several ships responding to its distress call, the ship ran aground and broke in two. It's entire payload was dumped into the English Channel.
8. Angola - 1991 - more than 51 million gallons
The tanker exploded, exact quantity of spill unknown
9. Italy - 1991 - 45 million gallons
The tanker exploded and sank off the coast of Italy and continued leaking it's oil into the ocean for 12 years.
10. Odyssey Oil Spill - 1988 - 40 million gallons
700 nautical miles off the cost of Nova Scotia.
I think you are right about the Greenpoint oil spill in Brooklyn New York is probably the worst on U.S. soil.
Greenpoint Oil Spill
The Greenpoint oil spill is one of the largest oil spills ever recorded in the United States. Located around Newtown Creek in the Greenpoint neighborhood of Brooklyn, New York City, between 17 million and 30 million gallons of oil and petroleum products have leaked into the soil from crude oil processing facilities over a period of several decades.
* 1 History of the area
* 2 Discovery of the spill
* 3 Cleanup efforts and seepage mitigation
* 4 Environmental litigation
* 5 References
* 6 External links
History of the area
Main articles: Greenpoint, Brooklyn and Newtown Creek
The areas of the northeast industrial section of Greenpoint along Newtown Creek were home to oil refineries from the 1840s, and by 1870 boasted more than 50 petroleum processing plants, many of which were incorporated into the Standard Oil Trust towards the end of the century. Standard Oil's successors (Mobil and later ExxonMobil) used the refining facilities until 1966 and later operated a bulk petroleum storage facility and a distribution terminal on the site until 1993.. Other petroleum companies operating in the area were Amoco (later BP) and Paragon Oil (now part of ChevronTexaco).
 Discovery of the spill
In September 1978 a United States Coast Guard helicopter on a routine patrol discovered a plume of oil flowing in the creek, originating from a bulkhead at Meeker Avenue. A subsequent study revealed the large-scale soil contamination, which was estimated in excess of 50 acres (0.20 km2) and a spillage volume of more than 17 million gallons.
...According to page 42 from an Environmental Protection Agency study, "the American Petroleum Institute (2002) indicates that 40% to 80% of a product spill may be retained in soils as residual product". The Department of Environmental Conservation's website states that petroleum companies participating in the cleanup have used a Free Product Recovery System for groundwater, rather than the soils.
On October 20, 2005, local residents within the area of the oil recovery operation, which is located in the predominantly commercial/industrial eastern section of Greenpoint near the East Williamsburg Industrial Park, filed a lawsuit against ExxonMobil, BP and Chevron in Brooklyn State Supreme Court, alleging they have suffered adverse health consequences. ExxonMobil asserts that the oil was spilled by Paragon Oil.
So it's possible that oil had been leaked on that site since 1840 (more likely sometime later), and wasn't discovered until 1978! The spilled oil has been there for decades, and of the 30 million gallons spilled there over an 100 acre area, only 9 million gallons have been recovered, and cleaned. The article I sited above claims environmental hazard of benzene gas is leaking into homes from the underground spill in enough concentrations to cause cancer over a long period of time.
It's a mess!