Who was the first Republican Party candidate to become president of U.S.?

There have been 19 Republican presidents, the first being Abraham Lincoln, who served from 1861 to 1865. He was assassinated in 1865.

President Lincoln led the United States through the Civil War. In doing so, he preserved the Union, abolished slavery, strengthened the federal government, and modernized the economy. Prior to being president, Lincoln in 1854 became a leader in building the Republican Party, which had a statewide majority in Illinois.

In 1860, Lincoln secured the Republican Party presidential nomination as a moderate from a swing state. He won the presidency although he gained very little support in slave holding states located in the South. He won states in the U.S. in the North and was elected president in 1860. Next, he had to face the Civil War as president which started in April 1861.