The District of Columbia, Oregon and Alaska will follow the lead of Colorado and Washington state, which approved legal marijuana by ballot initiative in 2012. But in the case of the District of Columbia, Congress can overrule the voters’ choice, and Representative Andy Harris, a Republican from Maryland, has signaled his intention to push Congress to do so.

Legalization in Colorado has produced mixed results since January. Crime in the state has continued to fall. But there have been some concerns regarding marijuana edibles, which the state public health department recently recommended prohibiting. And government revenues have fallen short of expectations, in part because many users continue to rely on Colorado’s lightly taxed medical marijuana system.

There is less data from Washington state, where legal sales did not begin until July.