July 31, 2015 7:00 AM EDT

It was 225 years ago Friday that Samuel Hopkins of Philadelphia was granted a U.S. patent for his new method of making potash, a salt useful for fertilizer. The patent was signed by George Washington, who had established the patent system mere months earlier.

Hopkins’ patent was the first such document in the nation’s history, but it was far from the last. As can be clearly seen by the documents and objects on show at Inventing in America—an exhibit that opened earlier this month at the Smithsonian’s National Museum of American History, in collaboration with the U.S. Patent and Trademark Office, and will be on view through 2020—the tradition of ingenuity in the United States has been a fruitful one. And that makes sense: as John Gray, the museum’s director, said in a statement, the U.S. itself was a new invention when it was founded.

It used to be required that a patent application come with a model of the idea, and now the museum has thousands of those models, along with prototypes and trademark examples. From the printing presses and typewriters of the 19th century, to DuPont Kevlar—celebrating its 50th birthday this year—and the Apple computer, here are some examples to get the inspiration going for the next big invention. (Sorry, a thinking cap isn’t one of them.)

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Write to Lily Rothman at lily.rothman@time.com.

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