The American economy in the 1990s was changing and growing at a rapid pace, particularly later in the decade. This pace would turn out to be unsustainable as it was built on something of a "bubble." After a recession in the early part of the decade (that helped get President Clinton elected), the economy took off as the internet fueled a boom. The changing technology in this and other sectors combined with rapid globalization and the rise of the service sector to drive economic growth.
Of course, this growth was not shared by all. Manufacturing jobs continued to be lost both to foreign competition and to technological changes. However, these losses were outweighed by jobs in new sectors of the economy. These factors made the late 1990s a very optimistic time in the US economy.