March for America is a registered trade name of the Sixteen Thirty Fund, a left-of-center advocacy organization managed by the for-profit consulting firm Arabella Advisors. March for America is one of almost 50 trade names that Sixteen Thirty Fund has registered, according to the organization’s 2018 tax returns. 
The left-wing advocacy group Sixteen Thirty Fund registered the trade name March for America on April 18, 2018 with the District of Columbia’s Department of Consumer and Regulatory Affairs.  The trade name was set to expire on April 12, 2020. 
Many of the Sixteen Thirty Fund trade names were for groups very active at the local and state level on behalf of Democratic congressional campaigns during the 2018 midterm elections, involved in criticizing Republican candidates through issue advocacy without direct endorsements. The individual groups had websites, Facebook pages, aired commercials and promoted volunteer efforts. Many listed staff and executives. 
However, March for America was among the Sixteen Thirty Fund projects that did not appear to have a much of an online presence and had no traceable list of staffing. March for America also does not seem to have been a specific event that took place, at least with regard to the Sixteen Thirty Fund.
Sixteen Thirty Fund
The Sixteen Thirty Fund often operates with charitable “sister” nonprofit New Venture Fund, an organization that sponsors various left-of-center organizations. Both Sixteen Thirty and New Venture are controlled by Washington-based philanthropy consulting group Arabella Advisors.
Politico referred to the Sixteen Thirty Fund as a “massive ‘dark money’ network” responsible for “boost[ing] Democrats” in the 2018 midterm elections.  The Atlantic called the Sixteen Thirty Fund one of the “key groups founded to resist [President Donald] Trump.”