when was it first discovered?
An unreactive gas was suspected to be a component of air by Henry Cavendish
Argon
An unreactive gas was suspected to be a component of air by Henry Cavendish in 1785.

Argon was first isolated from air in 1894 by Lord Rayleigh and Sir William Ramsay at University College London by removing oxygen, carbon dioxide, water, and nitrogen from a sample of clean air. They first accomplished this by replicating an experiment of Henry Cavendish's. 
where does argon come from and how is it extracted Nearly all of the argon in the Earth's atmosphere is radiogenic argon-40, derived from the decay of potassium-40 in the Earth's crust what is argon? It is a chemical element with the symbol Ar what can you tell me about it's place in the periodic table? It is in group 18 of the periodic table and is a noble gas why is it called so? It is derived from Greek, a neuter singular form of meaning "lazy" or "inactive", as a reference to the fact that the element undergoes almost no chemical reactions
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Argon [SEP] History
The difference was slight, but it was important enough to attract their attention for many months. They concluded that there was another gas in the air mixed in with the nitrogen. Argon was also encountered in 1882 through independent research of H. F. Newall and W. N. Hartley. Each observed new lines in the emission spectrum of air that did not match known elements.