what kinds of new economic opportunities drew migrants and immagrants to the west in the 2nd half

Three major causes: The Cattle Boom, The Minning Boom, and Land

The cattle boom ended abruptly in the 1880s. However, many early western towns were cattle towns or railheads. Cattle were initially herded in the open range by rangers. They were then driven miles and miles to the nearest railroad. The railheads, located in Oklahoma, South Dakota, Kansas, etc. attracted other occupations: preachers, teachers, prostitutes, inn keepers, etc.

The mining boom began with the discovery of gold in 1848. By 1849, many moved west to seek a fortunate. It is from this time we get terms such as "gold fever" and the "49ers". As a result, towns developed much like railheads.

Finally, the government encouraged westward expansion. In order to claim and hold the land they needed perminant settlers. The most effective means to do so was to give free land to the poor, who were willing to risk their life for a better existance.

Lookup: The cattle boom, mining boom and the homestead act.

I hope this helps.