Originally active in politics as a Jacksonian Democrat, he fell out with the party during the presidency of Martin Van Buren and eventually became a Whig.

[3] The defection of the conservatives was considered a harbinger for the 1840 presidential election, at which Van Buren was defeated by William Henry Harrison.

[3] On January 13, 1840, they reelected Tallmadge to the Senate, and indicated in their approved resolutions that the effective date was as of March 4, 1839.

[5] In the early 1840s, Tallmadge purchased a large tract of land in what became Fond du Lac, Wisconsin, in anticipation of constructing a home for his retirement.

Promising not to take an overly partisan approach, he advocated for the expansion of railroads, in keeping with the position he had taken as a state legislator and a U.S.

[6] He also argued against extending the naturalization period for Wisconsin citizenship to 21 years, and promoted experimental farms and agricultural societies.

[6] The legislature authorized printing and distribution of his message, including 750 copies in German, the first time Wisconsin legislators had ever taken such an action.

[7] Tallmadge decided to stay in Wisconsin, and built his planned residence in Fond du Lac, where he practiced law while living in semi-retirement.

[6] He also maintained a home in Washington, D.C., where he frequently traveled to serve as an unofficial ambassador for Wisconsin to the federal government and lobbyist for its interests.

[8] He had previously been a believer in premonitions, and claimed he had one that resulted in him narrowly escaped death aboard the USS Princeton when a cannon exploded and took the lives of five people.

[8] Tallmadge was also reported to be a believer in other supposed spirit communications, including the floor and table rappings that typically accompanied séances.

Through the Tallmadge family's many lines and descendants, Nathaniel is a distant cousin of Ernest Hemingway and Ben Affleck.

[13] The cemetery is now 60 acres and represents the final resting place for 24,000 people, including most of the most notable residents of Fond du Lac throughout history.

[14] He died in Battle Creek on November 2, 1864,[15] and was buried at Rienzi Cemetery in Fond du Lac.