By 1846, Mt. Pulaski had outgrown Postville, the county seat, and a movement was organized looking to the removal of the seat of justice to Mt. Pulaski. Mt. Pulaski at this time had over 300 inhabitants. Michael W. Swing, representative in the General Assembly, was prevailed upon to introduce a bill in that body providing for the submission to vote in Logan County of the proposition to remove the county seat from Postville (then called Camden) to Mt. Pulaski. This bill passed Feb. 23, 1847, and provided for an election on the first Monday in April. The removal was conditioned on the citizens of Mt. Pulaski erecting a courthouse building. At the election a majority favored the proposition of removal. The following year the courthouse was erected in the center of the public square, where it still stands today in complete preservation, the lower story being utilized for the post office and the upper story for the library. Particulars with reference to this courthouse and the history of the county, during the period the county seat of justice was at Mt. Pulaski, have been given in the chapter on "County Government."  The courthouse building cost $3,000, all but $300 having been contributed by the citizens of Mt. Pulaski. Mt. Pulaski continued to be the county seat until 1855 and during that period the town experienced a substantial growth. During court terms it was an exceedingly lively place, Lincoln, Douglas, Swett, Trumbull, Stuart and other great legal luminaries of former days being frequently in attendance. During the county seat period, many business buildings were erected around the square and in Mt. Pulaski as well as many private residences. In 1849, George Meister established a brickyard in the town and in the same year George and John Mayer opened up a store. In 1851, Samuel C. Beam built a sawmill and six years later erected a flouring mill in connection with the same. The first churches erected in the town were the Methodist and the First Lutheran Zion's church, both erected in 1852. New edifices have since been erected. By special act of March 4, 1854, the boundaries of the town were extended to include the additions platted and laid out subsequent to the original survey.

     The removal of the county seat from Mt. Pulaski to the new town of Lincoln, by virtue of a vote on the proposition submitted at the general election in 1853, has already been noted at length in the chapters on "County Government" and the "City of Lincoln," and need not be recounted here. It was, of course, a great disappointment to the citizens of Mt. Pulaski, but still did not daunt their civic pride and courage, and in a few years, the "mound" had substantially recovered from the shock.

     By act of the Legislature in 1857, the old court house was turned over to Henry Vonderleith, Jabez Capps and George W. Turley as trustees for two years, to be by them turned over to the Board of Education and soon thereafter, the building was utilized as a school building. In 1861, the Evangelical association erected what was the third church building in the town. In 1865, the First Lutheran society sold their church building to the Catholic denomination and one block from the old site erected their present house of worship, at a cost of $21,000.  The courthouse/school house continued until 1877.