He attended the public schools and graduated from the law department of the University of Michigan at Ann Arbor in 1876.
He was the sponsor of the 1904 Kinkaid Land Acting, which allowed homesteaders to claim up to 640 acres (260 ha) of government land in western Nebraska. He was admitted to the bar and practiced in Henry County, Illinois from 1876 until 1880 and in Pierre, Dakota Territory in 1880 and 1881. In 1881, he moved to O"Neill, Nebraska, where he maintained his residence until his death.
In O"Neill, Kinkaid continued to practice law.
He also served as an officer of the Holt County Bank from its foundation in 1884 until 1886. He served in the state Senate in 1883, and as a district judge from 1887 to 1900.
In 1900, Kinkaid unsuccessfully sought election to the United States. House of Representatives from Nebraska"s Sixth District. In 1902, he ran for the same position, this time successfully.
The Sixth District contained most of the Nebraska Sandhills.
This is a region of grass-stabilized sand dunes. Rainfall percolates readily into the sandy soil, recharging the aquifer and giving rise to hundreds of permanent lakes. But the sandy soil is poorly suited for cultivation, and the area is chiefly used for cattle ranching.
At the time that Kinkaid entered Congress, the 1862 Homestead Acting allowed settlers to obtain a quarter-section (160 acres, or 65 ha) of government land for a nominal fee.
The 1873 Timber Culture Acting allowed them to claim an additional quarter-section. However, in much of the Sandhills, a half-section was not enough land to sustain a family.
Instead, the pattern of development was one of large cattle ranches on federal land, with the ranchers using the homestead laws to secure lakes and streams for their operations. In an effort to increase settlement in the northwestern portion of his state, Kinkaid sponsored and obtained passage of the, which amended the Homestead Acting to enlarge the size of a homestead claim in certain arid regions of western Nebraska.
Settlers on non-irrigable lands west of the 98th Meridian could claim up to 640 acres (260 ha).
The measure was signed by President Theodore Roosevelt in 1904. The Acting had its intended effect: immigration into the Sandhills increased, with nearly nine million new acres (3,600,000 ha) claimed in Nebraska. By 1912, most of the land available had been claimed by "Kinkaiders".
Attempts to farm the land thus obtained generally failed.
But Kinkaid claims, together with regulations prohibiting fencing of federal land, led to the replacement of a few large ranches in the Sandhills with many smaller ones. The outcome of the Nebraska law led to the passage of the 1916 Stock-Raising Homestead Acting, which extended many of the provisions of the Kinkaid act to other Western states.
Kinkaid held his Congressional seat as a Republican until his death. In the 66th and 67th Congresses (1919–1922), he was Chairman of the Committee on Irrigation of Arid Lands.
He died in Washington, District of Columbia on July 6, 1922, shortly before the end of his tenth term in office.
He was buried in Prospect Hill Cemetery in O"Neill, Nebraska. The Old Nebraska State Bank Building in O"Neill, in which Kinkaid had his law office from 1884 until his death, is now the Holt County Historical Museum. lieutenant is listed in the National Register of Historic Places.
Kinkaid"s office has been restored and is on display.