Dockworkers at 36 ports across the eastern U.S. are now on strike for the first time in decades. And the work stoppage could snarl supply chains — leading to shortages and higher prices if it stretches on for more than a few weeks.

For the first time since 1977, 36 ports stretching from strategic seaboard locations as far north as Maine and as far south as Texas – all of which handle an aggregate $3 trillion in the country’s annual international trade – will be idle due to a work stoppage.