Be proud, my Race, in mind and soul;
Thy name is writ on Glory's scroll
In characters of fire.
High 'mid the clouds of Fame's bright sky
Thy banner's blazoned folds now fly,
And truth shall lift them higher.
Thou hast the right to noble pride,
Whose spotless robes were purified
By blood's severe baptism.
Upon thy brow the cross was laid,
And labour's painful sweat-beads made
A consecrating chrism.
No other race, or white or black,
When bound as thou wert, to the rack,
So seldom stooped to grieving;
No other race, when free again,
Forgot the past and proved them men

 Although it seems that Dunbar is being inclusive of all people of African descent, this statement implies that he distinctly means enslaved Africans, hence being bound to racks.
Ode To Ethiopia