Columbus Day is a federal holiday, which means most US government institutions are closed today. Yes, that means the post office, and banks, too, because they are federally insured.
Some states and cities abstain from observing the holiday, so we recommend calling ahead to the office or agency you want to know about. Many school districts give students the day off, and public transit in many cities will most likely run on reduced schedules.
Looking to capitalize on the long weekend, many retail stores are open for business, hoping to attract frugal shoppers with storewide sales.
The New York Stock Exchange is also open.