The members were pledged to uncompromising and unconditional loyalty to the Union, to complete subordination of political views to this loyalty, and to the repudiation of any belief in state rights.

The other large cities followed the example of Philadelphia and New York, and soon Leagues, connected in a loose federation, were formed all through the North.

They were social as well as political in their character and assumed as their task the stimulation and direction of loyal Union opinion.
As the Union armies proceeded to occupy the South, the Union League sent its agents among the disaffected Southern people.

Its agents cared for Negro refugees in the contraband camps and in the North.

In such work the League cooperated with the various Freedmen's Aid Societies, the Department of Negro Affairs, and later with the Freedmen's Bureau.