Answer:
to settle a trade dispute with another country
Some of the pull factor codes were things like the Homestead acts which were a series of acts on land allocation. For example, if you went westwards, the country would give you a huge piece of land which would become fully yours after five years of successful agricultural business.
Robert E. Lee was Lincolns first choice. Lee refused since his native state was Virginia, which was part of the Confederation.
It's talking about the first shot of the Revolutionary War