The corporate wards of the state typically have been returned to private hands after short, sometimes fleeting, stretches under federal stewardship.

Finance experts say that having Washington take stakes in United States banks now  like government interventions in the past  would be a promising move to address an economic emergency. The plan by the Treasury Department, they say, could supply banks with sorely needed capital and help restore confidence in financial markets.

Elsewhere, government bank-investment programs are routinely called nationalization programs. But that is not likely in the United States, where nationalization is a word to avoid, given the aversion to anything that hints of socialism.

In past times of war and national emergency, Washington has not hesitated. In 1917, the government seized the railroads to make sure goods, armaments and troops moved smoothly in the interests of national defense during World War I. After the war ended, bondholders and stockholders were compensated and railways were returned to private ownership in 1920.

During World War II, Washington seized dozens of companies, including railroads, coal mines and, briefly, the Montgomery Ward department store chain. In 1952, President Harry S. Truman seized 88 steel mills across the country, asserting that unyielding owners were determined to provoke an industrywide strike that would cripple the Korean War effort. That nationalization did not last long, though, because the Supreme Court ruled the move an unconstitutional abuse of presidential power.

In banking, the government took an 80 percent stake in the Continental Illinois Bank and Trust in 1984. Continental Illinois failed in part because of bad oil-patch loans in Oklahoma and Texas. As the nation’s seventh-largest bank, Continental Illinois was deemed “too big to fail” by federal regulators, who feared wider turmoil in the financial markets. In the end, the government lost an estimated $1 billion on the bad loans it bought as part of the takeover of Continental, which eventually became part of Bank of America.

The nearest precedent for the Treasury plan, finance experts say, are the investments made by the Reconstruction Finance Corporation in the 1930s. The agency, established in 1932, not only made loans to distressed banks, but also bought stock in 6,000 banks, at a cost of $1.3 billion, said Mr. Sylla, the N.Y.U. economist. A similar effort these days, in proportion to today’s economy, would be about $200 billion.