WASHINGTON — All but one of the nation’s 30 largest banks are better able to withstand a severe U.S. recession and global downturn than at any time since the financial crisis, the Federal Reserve has determined.

Results of the Fed’s annual “stress tests” showed Thursday that only Zions Bancorp failed to meet the Fed’s minimum level of capital to withstand a crisis. The results showed continued improvement in banks’ financial positions since the 2008 crisis, the Fed said. That built on positive results from last year’s tests.

The 30 banks tested included Bank of America, Citigroup, JPMorgan Chase and Wells Fargo.

The Fed has conducted stress tests of the largest U.S. banks every year since 2009, when the financial crisis plunged the country into the worst economic downturn since the Great Depression of the 1930s. The annual checkup is designed to measure how well the industry would fare in another severe recession. It aims to ensure that banks could keep lending during such a punishing stretch.

JPMorgan Chase, Morgan Stanley and Bank of America declined to comment on the outcome of their stress tests Thursday. Each planned to release the results of their own internal stress tests later in the day.

Goldman Sachs also declined to comment. A call to James Abbott, Zions Bancorp’s director of investor relations, was not immediately returned.

Under the Fed’s stress tests’ “severely adverse” scenario, the U.S. would undergo a recession in which unemployment — now at 6.7 percent — would reach 11.25 percent, stocks would lose nearly half their value and home prices would plunge 25 percent.