Build a better mousetrap, and the world will beat a path to your door is a phrase attributed to Ralph Waldo Emerson

Ralph Waldo Emerson

Ralph Waldo Emerson was an American essayist, lecturer, and poet, who led the Transcendentalist movement of the mid-19th century...

 in the late nineteenth century. The phrase is actually a misquotation of the statement:

In 1889, seven years after Emerson's death, came the invention of the current standard of mousetrap

Mousetrap

A mousetrap is a specialized type of animal trap designed primarily to catch mice; however, it may also trap other small animals. Mousetraps are usually set in an indoor location where there is a suspected infestation of rodents. There are various types of mousetrap, each with its own advantages...

s. That same year Emerson was quoted as saying:
The phrase has turned into a metaphor about the power of innovation, and is frequently taken literally, with more than 4,400 patents issued by the United States Patent and Trademark Office

United States Patent and Trademark Office

The United States Patent and Trademark Office is an agency in the United States Department of Commerce that issues patents to inventors and businesses for their inventions, and trademark registration for product and intellectual property identification.The USPTO is based in Alexandria, Virginia,...

for new mousetraps, with thousands more unsuccessful applicants, making them the "most frequently invented device in U.S. history".