The Act of Admission, effective May 11, 1858, admitted the State of Minnesota into the union.
Minnesotans surely expected that after enactment of the Enabling Act, the adoption of a constitution and election of a government in 1857, their state's admission would be swift and uncontroversial---a mere formality. Instead, it was subjected to days of debates that reflected the sectional tensions of ante-bellum politics.
Because Kansas was seeking admission as a slave state, several Southern senators wanted the two applicants to stand or fall together. Others objected that Minnesota was not a state, and that it had not complied with the Enabling Act. They complained that the senators and representatives who asked to be seated had been elected before the state was admitted, contrary to the correct procedure, which was admission followed by an election (three congressmen had been elected by the voters in October, and two senators by the legislature in December). Still others noted that the census required by the Enabling Act was not completed, and so it was unclear whether one, two or three congressman should be seated. The issue of "alien suffrage" resurfaced. Eventually, on April 7, 1858, under the shrewd guidance of Senator Stephen A. Douglas, the bill passed the Senate 49 to 3.
In the House, it ran into fierce opposition from John Sherman of Ohio, who called Minnesota's dysfunctional constitutional convention a "double-headed mob." Others renewed objections to alien and Indian suffrage. The debates raged about a week, ending on May 11, 1858, when the House passed the measure, 157 to 38. It was signed that day by President Buchanan.
Now a state, there remained the formality of admitting Minnesota's two senators and two representatives. Despite charges of fraud, Henry M. Rice was sworn, as was his colleague, James Shields. Later, Rice was exonerated by an investigation led by Jefferson Davis.
In the House, several congressman, led by John Sherman, raised many technical objections to the seating of William W. Phelps and James M. Cavanaugh, who had been elected in October 1857. After an investigation by the Committee of Elections, their credentials were accepted and they took the oath of office on May 22, 1858.
The complete text of the Act of Admission is posted here followed by Thomas F. Moran's account of its passage, published first in 1898 by the Minnesota Historical Society. Moran (1866-1928) later became a well-known professor of history at Purdue University.