Thomas Leiper Kane was the most influential and hardest working mediator between the branches of the U.S. government and the Mormon Church that the latter had during its early history.

Kane was born at Philadelphia on 27 January 1822 to Judge John Kintzing Kane and Jane Duval Leiper. In 1840 he went to Europe to recover his health, and while there he acquired a greater appreciation for America's freedoms. After his return, he worked at several, mostly short-lived, government positions. He also worked for the underground railroad prior to the Civil War, smuggling slaves to northern states.

In May 1846 Mormon Elder Jesse C. Little was going through Philadelphia to Washington, D.C., and stopped to address a Mormon conference. Thomas Kane was there out of curiosity, and he became interested in the Mormons going to California. Little and Kane discussed Mormonism for several hours, and Kane became desirous of helping the church. Separately, Little and Kane traveled to Washington, D.C., where the Kane introduced Little to government officials. Little reported to Brigham Young, "from some cause he feels very much interested in behalf of our people."

On 12 June 1846 both Kane and Little took the train to St. Louis. From there, Kane went briefly to Fort Leavenworth, and left bringing information about the need for the Mormon troups. He then traveled to the Mormon habitations in Iowa, reaching the area about one month later. On 17 July a meeting was held at that place to create the Mormon Battalion.

Captain James Allen, in charge of battalion enlistment, gave the Saints temporary permission to travel through and live in the Pottawattamie Indian lands. Colonel Kane helped arrange official recognition with the U.S. government. In spite of correspondence which lasted eighteen months, permission was not granted for Mormon congregation in the Omaha Indian area.

During the first week in August 1846, Kane became seriously ill. At his request, to counteract possible charges of Mormon abuse, a letter was written asking for a doctor to come from Fort Leavenworth. Dr. J.S. Edes came, treated Colonel Kane for fever, and verified his condition with army officials. Kane recovered within a month. He soon left the Mormon settlement to return east, on the way visiting Nauvoo shortly after the last Saints had left that city, and he later expressed his impressions of it. In honor of his intercession between the government and the Indians, a Mormon settlement in Iowa was renamed Kanesville in 1848.

After returning to Philadelphia, Kane continued his efforts to secure Mormon rights. The first Mormons had reached the Great Basin in 1847 and their leaders soon consulted Kane concerning his views of self-government. In early 1849, he recommended that they establish a territorial government, thinking that they would be able to choose their own officers under a favorable presidential administration; but by November of that year Kane had reversed his opinion, knowing that the federal government would likely send oppressive outsiders. Of course, in 1850, Utah did become a territory, and Kane's thoughts came true. He also continually advised neutrality as to partisan politics, feeling that favoritism toward one party would alienate the other side in future dealings.

On 26 March 1850 Kane delivered an important lecture (of more than thirty written pages) before the Philadelphia Historical Society on the subject of the Mormons. He described their trials and tribulation, the desolation of Nauvoo, and their westward trek. Six months later, he defended Brigham Young in the eastern newspapers against spurious charges and gave recommendations and information about the Mormons to President Fillmore.

With the beginning of territorial status, angry appointed officials had begun to send negative reports back to Washington. The situation festered and, compounded by the political turmoil of the era, President James Buchanan decided in 1857 to send an army to subdue the supposedly rebellious Mormons in Utah. Six months later, on 31 December 1857, Kane was appointed an envoy to assess the Mormon attitudes and placate them if possible. Kane sailed from Pennsylvania on 4 January under the name of Dr. Osborne, to the Isthmus of Panama, which he crossed by railroad. He resumed his trip by ship to San Francisco, and arrived there 29 January. He continued on through the Mormon city of San Bernardino and on to Salt Lake, reaching the city 25 February 1858. That day at a conference with Brigham Young, Kane was told, "Friend Thomas, the Lord sent you here, and he will not let you die. . . . I want to have your name live to all eternity. You have done a great work and you will do a greater work still."

After consulting with Brigham Young for two weeks, Kane left on 8 March for negotiations with Colonel Johnston and newly appointed territorial governor Alfred Cumming at Fort Bridger. After smoothing some ruffled feathers, it was arranged that Cumming would accompany Kane back to Salt Lake without the army; and they arrived 12 April 1858. It was then settled that Cumming would be accepted as governor of Utah, the army would move through Salt Lake to an outlying location without disturbing the city, and commissioners would be sent to work out a peace plan.

Although on 24 April Kane received news that his father had died, he remained in Salt Lake City until 13 May discussing philosophies with Brigham Young, who later observed that "your views are so different from ours" in spite of his support. Kane then returned back east and made his report to President Buchanan.

From that time Kane's direct assistance to the Mormons declined, although he remained friendly towards them all his life. During the Civil War, Kane raised some recruits, and fought bravely until resigning 7 November 1863 from wounds and poor health. He was raised to the rank of general after the war. Kane continued corresponding with Brigham Young and in 1872 was invited to take a trip through the Utah settlements to St. George. His wife, Elizabeth, described this trip in Twelve Mormon Homes. Kane also had writing aspirations, desiring to write a biography of Brigham Young and a history of the Mormons in general, but he never accomplished either.

Kane retired to private life and died 27 December 1883. He had been warmly recognized through Mormon letters dozens of times during his life, such as when Wilford Woodruff wrote to him on 8 March 1859: "The name of Colonel Thomas L. Kane stands most prominent, . . . an instrument, in the hands of God, and inspired by him, to turn away, in 1858, the edge of the sword, and save the effusion of much blood, performing what the combined wisdom of the nation could not accomplish, and changing the whole face of affairs, the effects of which will remain forever. Your name will of necessity stand associated with the history of this people for years to come, whatever may be their destiny."