John brown, harriet tubman, harriet beecher stowe, stephen douglas, all opposed slavery. who do u think had the greatest impact on american history and why? ?

I think it was Harriet Tubman, as she was born a slave and understood what it meant to be a slave, she had to escape in 1849 and her motive to help slaves was a powerful one "Families should not be separated". 
She became the most famous conductor on the Underground Railroad. She helped many slaves individually as well as formed a network to help them through other activists. 

what the first or next guys says

north atlantic treaty organization.