The Union League was able to muster such a large membership as many Northern men remained home while immigrants, former slaves, draftees and substitutes were off fighting Americans in the South. The Union League became a powerful propaganda arm of the Republican Party and an effective instrument of political control in the postwar South.
Bernhard Thuersam, www.Circa1865.com
The Strong Economic Interest of the Union War Effort
“The first Union League was founded in Pekin, Illinois, by a Republican party activist, George F, Harlow. As war weariness deepened, and the restraint that had held back dissenters in the early months of the war fell away, loyal Republican became alarmed by the resurgence in support for the Democratic Party. To combat this, they formed a secret society “whereby true Union men could be known and depended on in an emergency.” By the end of 1864 the Leagues claimed more than a million members.
In May 1863, the [Philadelphia] Press urged that the north unite “by any means” and called on Unionists to “silence every tongue that does not speak with respect of the cause and the flag.” Union Leagues institutionalized the denial of legitimate partisanship by conflating opposition to the Union [Republican] Party with disloyalty to the United States. “Men of the Northwest! Are you ready for Civil War?” asked an editorial in the radical Chicago Tribune, “the danger is imminent; the enemy is at your door . . . a Union Club or league ought to be formed in every town and placed in communication with the State central committee.” They formed vigilante groups, which reported suspected disloyalists to the War Department and called for the suppression of opposition newspapers. Leagues also mobbed the offices of several small-town newspapers whose editors had expressed support for Democratic candidates or had attacked the [Lincoln] administration.
Unlike the mass-membership Union Leagues, the Union League of Philadelphia, the New York Union League Club, and the Boston Union League Club were founder with the appropriate accoutrements of a mid-Victorian gentlemen’s club: elegant headquarters with libraries, billiard rooms and butlers. Membership was by invitation only and determined by social status and “unqualified loyalty to the Government of the United States and unwavering support for the suppression of the rebellion.” The idea was to exclude anyone suspected of Southern sympathies from business or social relations with members.
“Sympathy with [armed rebellion] should in social and commercial life be met with the frown of the patriotic and true. Disloyalty must be made unprofitable.” [A founding member of the Philadelphia club] . . . the issue of the war was, after all, one that directly confronted the class interests of the city’s business elite. “We . . . live under the national law. If that is broken down, our interests, our property, and our lives may be lost in the disorder that will ensue . . . Nothing but ruin awaits all business interests of ours . . . if the doctrines of the Secession leaders are to prevail” Sustaining the federal government was essential . . . [and] Furthermore, as bankers and the monied elite of New York assumed an ever-greater responsibility for financing the war effort through buying government bonds, there was also a strong economic interest in the success of the Union war effort.
(No Party Now, Politics in the Civil War North, Adam I.P. Smith, Oxford University Press, 2006, pp. 68-74)