In which statement is the transition used correctly?

1. Gold in California ignited interest in a railroad to reach the West. As a result, Americans disagreed on where to build the railroad.

2. Gold in California ignited interest in a railroad to reach the West. However, Americans disagreed on where to build the railroad.

3.Gold in California ignited interest in a railroad to reach the West. Therefore, Americans disagreed on where to build the railroad.

4.Gold in California ignited interest in a railroad to reach the West. Before this, Americans disagreed on where to build the railroad.