Historically speaking, the Populist Movement specifically emerged in the late nineteenth century, but it evolved out of various earlier movements centered around agricultural communities. Probably the most important and influential of these influences was the Granger Movement, which initially had the aim of protecting farming communities against the predatory techniques of the railroads. By mobilizing politically, the Grangers tried to achieve government intervention with the aim of having the railroads reclassified as a utility, subject to regulation.
However, one can trace this evolution even further back in time, toward the Jacksonian Revolution and particularly Andrew Jackson's war against the National Bank. It might even bet raced back to the first political parties and the division between the urban, commercially focused Alexander Hamilton and the more rural leaning Thomas Jefferson. In certain respects, Populism seems to be just one in a long line of manifestations on this larger historical trend.
Populism emerged during the Gilded Age, in a context of rapid industrialization and urbanization, but also one of general economic deflation. The later of these trends proved to be particularly unpleasant where farmers were concerned, given that they tended, by and large, to owe debts to banks and commercial interests, with the effects of deflation making it more onerous to pay back their lenders.
At the same time, the Second Industrial Age was also one of widespread exploitation: it was an era where the first union movements were still coming into being (and facing widespread hostility and mistrust) and government had yet to impose regulations concerning such themes as workplace safety or a minimum wage.
The Populist Movement, or People's Party, originated in the agrarian centers of the country, while also reaching out towards the urbanized working classes. Its primary goal was to switch the national currency standard to silver, a cheaper alternative to gold, which would produce inflation (to the benefit of farmers). At the same time, it introduced reforms such as the initiative, referendum, and recall, as well as election of senators by the popular vote. However, while it claimed to defend the interests of the working class, attempts at securing an alliance with urban populations was doomed to failure, given that these inflationary policies would have been disastrous to their own interests and financial security.
While the Populist Movement made real electoral gains in its lifetime, it ultimately failed to rise above its origins as a third party, and it swiftly went into decline. At the same time, however, certain aspects of its platforms (particularly its government reforms) were championed by the Progressives in the early twentieth century and remain in place in American politics today.
At the same time, it has had a legacy in entering the cultural lexicon, with the word populism still being used today, often pejoratively, to apply to all manner of popularly supported political movements whose ideologies and platforms (while popular) would be short-sighted or destructive when put into practice.