The March for Science is scheduled to take place April 22, 2017 in DC . Hashtag #ScienceMarch
Web site here, though not much there yet, this was JUST announced seconds ago.
Please note that they are accepting donations. Click through to the donations page to give a donation!
Alternate logo here:
To find out about other marches in your area, if you can’t get to DC, for now, look at March for Science “follow” list, here. They will be putting info up at a later time, apparently.