To remove people from a board, open the "Board Member" menu in the top right of the screen.
Click on the persons name you want to remove to view their board settings. If you are the "Owner" of the board, you will see the "Remove User" option. Click "Remove User" then confirm removal.
Repeat this step for all people you want to remove from the board. You can remove pending or active people on the board.
When a person is removed from a board, they will be removed from any tasks they were assigned to. All other information associated to the person will remain on the board. This information includes tasks, comments, file attachments, sub tasks, start dates, due dates, activities, and descriptions.