Patent of a straight and curved objects: the paperclip

The modern paper clip was patented on November 9, 1899 to William D. Middlebrook of Waterbury, Connecticut. Middlebrook invented not just the paper clip but he also invented a machine to produce the paper clip.

Cushman and Denison  purchased the Middlebrook patent in 1899. That same year Cushman and Denison also trademarked the name "GEM" for their new paper clip. 

Definition: paper clip, gem clip, paperclip
Function: A paper clip is a device which holds several sheets of paper together

Pressure: it leaves the paper intact and can be easily removed. 
Patent: 636,272 (US) issued November 7, 1899
Inventor: William D. Middlebrook 
Criteria: First practical. Modern prototype
Nationality: American

Timeline:

1867 Samuel Fay invents and patents a Ticket Fastener that also can be used to hold paper
1899 William D. Middlebrook invents and patents paper clip and the production machine
1899 Middlebrook sells patent to Cushman & Denison
1899 Cushman & Denison trademark the name GEM for their paper clip
1901 Johan Vaaler patents paper clip
1903 George McGill patents a paper clip that looks very similar to today's version

To read more: http://www.ideafinder.com/history/inventions/paperclip.htm