What do you know about the Fourth of July?

Americans are so committed to their Fourth of July barbecues that 44 million of them will travel more than 50 miles today to celebrate with family and friends.

Many also honour veterans with holiday parades and set off huge firework displays to mark their freedom. Here are five facts about the 4th of July to impress your American friends:

A six-tonne hoagie

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What better way to celebrate independence than with six-tonnes of meat and cheese stacked on 23,000 six-inch rolls? Philadelphia kicks off its 4th of July celebrations - called Wawa Welcome America! - on Independence Mall with "Hoagie Day". The opening ceremony features concerts but the main event is a sandwich served to 20,000 people in less than 60 minutes.

$7bn (£5.4bn) on beef and burgers

The US spends $7bn (£5.4bn) on food during the 4th of July holiday weekend. The main purchase is beef -- specifically $804m (£620m) on burgers, Buzzfeed reports. Americans spent $43m (£33m) last Independence Day on barbecue sauce, topping its competitor condiments of ketchup ($37m/£29m) and mustard ($25m/£19m). What do they put it on? A lot of it is squirted on 150 million hot dogs, long enough to make a line from Washington, D.C., to Los Angeles five times over, the Washington Examiner says.

Health concerns

Largely because of the fireworks displays, concentrations of fine particulate matter typically reach their highest hourly levels from 9pm-10pm on 4 July, with concentrations 42 per cent greater than on the days before and after Independence Day, EurekAlert says. The Environmental Protection Agency recommends people sensitive to particle pollution try to limit exposure by watching fireworks from upwind.

Wrong date?

Did you know that the US may celebrate the 4th of July as a national holiday, but the date isn’t quite accurate? The founding fathers signed their intent to declare independence from England on 2 July, but it wasn’t until 4 July that the Declaration of Independence was accepted by Congress, CBS News reports. John Adams wrote home to his wife Abigail on 3 July, saying that 2 July “will go down in history” - and it did, just two days later.

Firework displays

Fireworks are the staple of the weekend celebration, with huge shows in all major US cities, dating back to the first fireworks display for Independence Day in 1777.

Today, most fireworks are imported from China, with the US spending $296m (£229m) a year on the fireworks market. But the original fireworks to blast off were roasted bamboo stalks that blackened, sizzled and exploded, TIME reports.