Last year was a record-setting year for cheap gasoline prices, and 2016 is on trend to be even better.

Just days into the new year, the national average price at the pump was reported to be right under $2 per gallon for regular unleaded gasoline, the lowest it's been since March 2009, according to the AAA Fuel Gauge Report. Lower crude oil prices are largely responsible for the drop in gasoline prices; the price of crude has "roughly been cut in half since June 2014," according to The New York Times. (In December, Brent crude was trading at $36 a barrel).

Let's see how the states stack up.

Related: Here's Why the Price Of Oil Is Dropping

GASBUDDY - gasbuddy.com

California, Hawaii, and Nevada have the highest fuel prices in the nation as of January. California is number one, with a state average of $2.87 per gallon. In addition, 13 of the 15 cities with the highest gas prices in the nation are in California.

AAA Fuel Gauge Report - aaa.com

States in the West have some of the highest gas prices in part because of the cost of transporting gasoline: Refineries tend to be spread out in the West, the Atlantic reported. For example, even though Alaska produces a lot of crude oil, that oil must travel to the rest of the United States to be refined and then shipped back as gasoline.

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Other factors include special state regulations on gasoline: California requires a low-pollution blend of fuel that can only be produced at state refineries; if there's a shortage, the state can't import gasoline from other states because it won't meet the regulatory standards, and that drives up the price.

State taxes also factor into the price. Pennsylvania has the nation's highest gas tax, at 51.6 cents per gallon, followed by New York (45.99), Hawaii (45.10) and California (42.35), according to the Tax Foundation.

States with the lowest average gasoline prices are found mainly in the South and Midwest. Missouri tops the list of states with the lowest national average price of gas, at $1.70 per gallon, followed by Oklahoma, South Carolina, Arkansas, and Alabama.

States with the cheapest gasoline have more capacity to refine oil into gasoline, or they border states that do.

Overall, the nation's refineries can process 16.7 million barrels of oil per day. But some of the states with the cheapest prices can refine more than 300,000 barrels per day, according to 24/7 Wall St. For example, Louisiana and Texas have the largest refining capacity in the nation, with Texas refining more than 4.75 million barrels of oil a day.

Not to mention that the state gas tax for these states are some of the lowest in the nation.

American Petroleum Institute/Tax Foundation - taxfoundation.org