A Brief History of the Gas Tax in Washington State — and Why It Still Matters

​A Brief History of the Gas Tax in Washington State — and Why It Still Matters

​A Brief History of the Gas Tax in Washington State — and Why It Still Matters

The gas tax might seem like just a few extra cents per gallon, but in Washington State, it plays a crucial role in how we build and maintain our roads. The story behind the gas tax—and how Washington uses it—is also tied to one of the most important pieces of state law: the 18th Amendment to our state constitution.

The Origin of the Gas Tax in Washington

Washington was an early adopter of the gas tax. The state enacted its first gas tax in 1921, at 1 cent per gallon. The goal was simple: find a way to pay for road construction and maintenance as automobiles became more common. Over the years, that rate steadily increased to keep up with inflation and the growing need for highway infrastructure.

By 2023, Washington’s gas tax stood at 49.4 cents per gallon, making it one of the highest in the nation—ranking third after California and Pennsylvania. Add the federal gas tax (18.4 cents), and drivers in Washington pay nearly 68 cents per gallon in combined fuel taxes.


Here’s a quick look at how Washington stacks up:
State                                         State Gas Tax (Approx.)
California                                       ~58 cents
Pennsylvania                                 ~57 cents
Washington                                    49.4 cents
Oregon                                         ~38 cents
Idaho                                            ~33 cents
National Avg.                                ~30 cents

Washington consistently ranks in the top five for state gas taxes. The high rate reflects the state’s heavy investment in transportation infrastructure—and a legal requirement that restricts how those dollars can be spent.

The 18th Amendment: Protecting Transportation Funds

In 1944, Washington voters approved the 18th Amendment to the state constitution. It says that money collected from gas taxes and vehicle license fees must be used only for highway-related purposes. That means:

• Building and repairing roads and bridges
• Policing highways
• Paying off bonds for road construction

It cannot be used for:

• Public transit (like buses or light rail)
• Bike or pedestrian projects
• General government expenses

This restriction makes Washington’s transportation funding system fairly rigid. Even as many people call for greener, multimodal transportation options, the 18th Amendment locks gas tax revenues into road-focused uses.
Why It Matters for the Future

As cars become more fuel-efficient and electric vehicles (which don’t use gas at all) become more common, gas tax revenues are declining. But because of the 18th Amendment, replacing that revenue with something like a road usage charge (RUC) or mileage tax would require either a constitutional amendment or new legislation crafted to work within existing rules.

Lawmakers and policy advocates are already debating how to modernize transportation funding. But any major changes will need to reckon with the legal and historical legacy of the gas tax and the 18th Amendment.

Want to know more about upcoming proposals to change how transportation is funded in Washington? Stay tuned—2025 might be a turning point.