Answer: The transcontinental railroad and free land in the West.
The Republican party encouraged the construction of a transcontinental railway. The first transcontinental railway was built between 1863 and 1869. It was known as the "Pacific Railroad," and it was significant to the expansion of trade, commerce and travel in the country.
Land grants were also proposed by the Republican party several times before the Civil War, but they were only approved after the Southern States seceded from the Union in 1861. Known as the Homestead Acts, they were signed into law by Abraham Lincoln in 1862, leading to the distribution of 1.6 million homesteads representing 10% of all land in the United States.