A best interest plea means that  a defendant does not admit guilt to any offense, but agrees that a guilty plea is in his best interest under the circumstances. The defendant is sentenced, while still able to disagree with the prosecutor's description of events.
The transcontinental railroad began in Omaha, Nebraska and ended in Sacramento, California. Two companies built the railroad. The Union Pacific Railroad company began laying track from Omaha to the west while the Central Pacific Railroad company headed east from Sacramento. They both met at the middle in Promontory, Utah on May 10, 1869.
With the California Gold Rush and the opening of the West came an increased interest in building a transcontinental railroad. To this end, the Central Pacific Railroad Company was established, and construction of the route East from Sacramento began in 1863.