The Pro Football Hall of Fame is clearly trying to send a message when it comes to the flag -- the more, the better.
TMZ Sports has learned ... organizers at the HOF in Canton, OH recently planted more than 300 U.S. flags on the lawn as part of a campaign called "Huddle Up, America."
The HOF says the flags are "a sign of unity to bring all Americans together" -- and the campaign was designed to help the football community "work through issues that are important to our families, community and country."
Guessing Trump approves.