PORTLAND – A nationwide tour to showcase hydrogen-powered cars kicked off Monday.

The tour, which started at Fort Allen Park in Portland, is organized by the U.S. Transportation and Energy departments, the National Hydrogen Association and the California Fuel Cell Partnership.

Cars from nine manufacturers are taking part in the two-week, cross-country event that includes 31 stops in 18 states.

The aim of the tour is to highlight progress made in the development of hydrogen vehicles and fueling technologies. Hydrogen vehicles made by BMW, Daimler, Ford, General Motors, Honda, Hyundai-Kia, Nissan, Toyota and Volkswagen will be featured on the tour. Also participating are hydrogen fuel providers Linde, BMW’s hydrogen fuel partner for the tour, and Air Products, according to a press release.

“BMW has already logged nearly 2 million miles in our fleet of 100 BMW Hydrogen 7s. Being on this tour will show more people that hydrogen is truly the best alternative transportation fuel. An internal combustion engine, powered by hydrogen should play an important role in the future of sustainable mobility,” said Tom Baloga, BMW Vice President of Engineering, U.S., in a BMW press release on the tour.

The tour will visit key members of Congress in their home states to allow them the opportunity to see and drive these cars.

BMW Hydrogen 7 is the only car on the tour that stores liquid hydrogen to power an internal combustion engine, according to the press release. Hydrogen is one of the cleanest energy sources available producing zero emissions, with essentially the only tailpipe emission is water vapor, the industry release said.