Subway, the largest fast-food chain in the US and in the world, first opened in the 1960s and quickly expanded in the following decades.

Successful ad campaigns with Jared Fogle — the man who said he lost over 200 pounds while eating Subway sandwiches — and the "$5 footlong" jingle have contributed to sales throughout the years.

However, the company took a turn in 2014 when sales started to decline.

It had a public-relations crisis on its hands when Fogle was arrested and charged with having sex with minors and distributing and receiving child pornography. He was sentenced to nearly 16 years in prison in 2015.

In the past year, Subway closed over 1,000 locations nationwide.

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In the past few years, Subway restaurants have been dealing with growing pains, declining sales, and a public-relations issue with legal troubles for Jared Fogle, its former spokesman. As a result, the sandwich company has been closing hundreds of stores all over the US for the past few years.

But it hasn't always been like this. In the '80s, '90s, and early 2000s, Subway was expanding rapidly, becoming the world's largest fast-food chain.

Keep reading to learn how a company that was on the rise for decades suddenly took a turn for the worse.