Well, sort of. The Republican Party was formed when disgruntled members of the Whigs, Free Soil, Know-Nothings, and anti-slavery Northern Democrats defected and decided to form their own party. The only thing the defecting members of these four parties had in common was they were all anti-slavery people. The creation of the GOP was not a "merger" of those previous parties and didn't abolish them, it just took a significant chunk of their support.
In 1856, the Republican Party ran one ticket (Fremont/Dayton) while the Whigs & Know-Nothing Party ran a different joint ticket (Fillmore/Donolsen). The Republican Party, only two years old, got more votes for President than what was left of the Whigs/Know-Nothings and they went extinct shortly afterwards.
The GOP didn't adopt their familiar plank on immigration (control the borders, deport illegal aliens and make sure legal immigrants fully assimilate before they are granted citizenship) until the 1880s. Of course that still means the GOP has held the limited immigration position for about 125 years.
Celebrating a Century and a Half of Civil Rights Achievement by the Republican Party
Republicans held our first state convention in Jackson, Michigan on July 6, 1854. That fall, the GOP swept to victory throughout the North. Other anti-slavery Members of Congress joined the party, so that less than two years later, on February 2, 1856, Republicans elected a Republican Speaker of the House. The Republican National Committee first met the next month, to coordinate opposition to the pro-slavery policies of the Democrats, also known then as "slaveocrats."
And that summer, Republicans held our first national convention. There, we nominated our first presidential candidate, the Georgia-born form California Senator John Fremont. Four years later, we won the White House for the "Great Emancipator."
As the nation sacrificed during the Civil War, Republicans planned the most significant amendments ever to our Constitution and enacted - despite fierce opposition from the Democrats - the 13th Amendment to ban slavery, the 14th Amendment to protect all Americans regardless of the color of their skin, and the 15th Amendment to extend voting rights to African-Americans. The Republicans' 1875 Civil Rights Act guaranteed equal access to public accommodations without regard to race. Struck down by the Supreme Court in 1883, this law would be reborn as the 1964 Civil Rights Act.
"Every man that wanted the privilege of whipping another man to make him work for nothing, and pay him with lashes on his naked back, was a Democrat. Every man that raised bloodhounds to pursue human beings was a Democrat. Every man that cursed Abraham Lincoln because he issued the Emancipation Proclamation was a Democrat." - Robert Ingersoll, 1876.
For its first 80 years, the Republican Party was the only one to provide a home for Afican-Americans. Until well into the 20th century, every African-American Member of Congress was a Republican. The same was true for nearly all state legislators and other elected officials.
What's mostly interesting to me is how much more open and fluid political parties were back then. For instance, I doubt if many people know that Lincoln ran under the National Union Party ticket in 1864, as the Radicals took over the Republican party and looked to run him out.
The entire monolithic nature of political parties now was not at all present then. It was very much a dynamic political scene, and stayed that way until early in the 20th century.