Vertical well hydraulic fracturing was first used in 1949.
Horizontal hydraulic fracturing has developed since 1976.
Hydraulic fracturing was used in Austin Chalk in late '80s.
By the late '90s, “slickwater fracturing” of shales using various toxins, carcinogens, and radioisotopes was used.
The Energy Policy Act of 2005 (“Halliburton loophole”) removed protective restrictions on slickwater fracturing.
Controversies about fracking's safety have since erupted.
http://en.wikipedia.org/wiki/Exemptions_for_hydraulic_fracturing_under_United_States_federal_law
http://en.wikipedia.org/wiki/Environmental_impact_of_hydraulic_fracturing_in_the_United_States