The Federal minimum wage is $7.25. Many States have that same minimum wage and many have a higher minimum wage. Cities can also set a minimum wage. The higher of any of these is the legally required minimum wage in that jurisdiction. In other words Cities and States can set a minimum wage that is higher then the Federal rate. Cities and/or States cannot set a minimum wage which is lower than the Federal rate.
The Oregon Legislature recently passed a highly contested and complicated minimum wage. The six-year plan would raise wages starting this July, to $9.75 in urban areas and $9.50 in a lower, rural tier. Increases would top out in 2022 at $14.75 inside Portland's urban growth boundary, $13.25 in midsize counties and $12.50 in so-called "frontier" areas.
Bernie Sanders, Presidential candidate has proposed a $15.00 minimum wage. Should Congress pass a $15.00 minimum wage, it will become the legally required rate in all states. General consensus is that this won't happen. If the elected President endeavored to set the National minimum wage by executive order, all hell would break loose. Don't look for this to happen.