The decision is expected to have global implications, some of which may take years to play out. Here are some effects Americans can expect to feel as a result of so-called "Brexit."
On balance, about half of most Americans' retirement funds are invested in stocks, and they are expected to take a beating on the worry that the British decision to leave the EU will destabilize the global economy and torpedo corporate profits.
Early Friday, equity index futures were pointing to declines in excess of 3 percent for major U.S. benchmark indexes like the Standard & Poor's 500 .SPX and Nasdaq Composite .IXIC.
While Treasury bonds are rallying on the result, courtesy of their status as a global safe-haven asset, those price gains mean that already meager bond yields are going even lower. This diminishes their ability to deliver substantial income for investors and savers.
MORTGAGE RATES AND HOME PRICES
One upside could be for would-be homeowners, or those looking to refinance or with adjustable-rate loans. For them the cost for buying a house is likely to drop, at least in the near term.
Even before the Brexit vote, the average interest rate for a 30-year fixed-rate mortgage was at its lowest since May 2013 at 3.76 percent, according to the Mortgage Bankers Association.
On Friday the yield on the 10-year U.S. Treasury note US10YT=RR, to which most mortgages are indexed, dropped to below 1.50 percent, meaning borrowing costs for home purchases should head lower as well. The last time the 10-year note yield was this low was 2012, and that coincided with the average 30-year mortgage rate briefly dropping below 3.5 percent, the lowest in the post-World War Two era.
That could add fuel to a pretty hot U.S. housing market. Existing homes are selling at their fastest rate since 2007, while sales of new homes are proceeding near their most brisk pace since 2008. Home prices in the 20 largest metropolitan areas are, on average, the highest since late 2007.
The U.S. dollar is rising sharply, which could put the brakes on U.S. exports, damaging the sales and profits of dozens of multinational companies based in the United States.
Add to that the fact that Britain is the No. 5 buyer of U.S. goods and services, totaling about $56 billion last year, according to the U.S. Census Bureau. The British pound has plummeted by the most ever in a single day, about 8 percent, to its weakest level in three decades, and that will make U.S. products substantially more expensive in the United Kingdom.
But that's not all. The dollar has also surged by nearly 3 percent against the euro, and the EU is an even bigger export market for the United States, totaling $272 billion last year.
That spells trouble for the hundreds of U.S. companies with substantial revenue from Britain and the rest of Europe. Non-U.S. sales will now be worth less when translated back into dollars. U.S. corporate profits are already in the fourth consecutive quarter of year-over-year declines, to which the dollar's strength over the last three years was a significant contributor. A renewed bout of dollar strength risks extending that slump.
On the upside, traveling to Britain and the rest of Europe is likely to become noticeably cheaper.