<P> Pretty Little Liars is an American teen drama mystery thriller television series developed by I. Marlene King, loosely based on the popular book series of the same name by Sara Shepard . The show premiered on June 8, 2010 on ABC Family and ended on June 27, 2017, for a total of seven seasons and 160 episodes . </P> <P> The series spawned two spin - offs: Ravenswood (2013--2014) and the upcoming Pretty Little Liars: The Perfectionists . </P> <P> Set in the small suburban town of Rosewood, Pennsylvania (not far from Philadelphia), the series follows the lives of five girls: Spencer Hastings, Alison DiLaurentis, Aria Montgomery, Hanna Marin and Emily Fields, whose clique falls apart after the leader of the group, Alison, goes missing . One year later, the remaining estranged friends are reunited as they begin receiving messages from a mysterious villain named "A" or "A.D.", who threatens and tortures them for the mistakes they have made before and after Alison was alive . At first, they think it is Alison herself, but after her body is found, the girls realize that someone else is planning on ruining their lives . </P> <Table> <Tr> <Th_colspan="2"> Season </Th> <Th_colspan="2"> Episodes </Th> <Th_colspan="2"> Originally aired </Th> <Th_colspan="2"> Nielsen ratings </Th> </Tr> <Tr> <Th> First aired </Th> <Th> Last aired </Th> <Th> Viewers (in millions) </Th> <Th> Adults (18 - 49) </Th> </Tr> <Tr> <Td> </Td> <Td_colspan="1"> </Td> <Td_colspan="2"> 22 </Td> <Td_colspan="1"> June 8, 2010 (2010 - 06 - 08) </Td> <Td> March 21, 2011 (2011 - 03 - 21) </Td> <Td> 2.87 </Td> <Td> 1.0 </Td> </Tr> <Tr> <Td> </Td> <Td_colspan="1"> </Td> <Td_colspan="2"> 25 </Td> <Td_colspan="1"> June 14, 2011 (2011 - 06 - 14) </Td> <Td> March 19, 2012 (2012 - 03 - 19) </Td> <Td> 2.68 </Td> <Td> 1.0 </Td> </Tr> <Tr> <Td> </Td> <Td_colspan="1"> </Td> <Td_colspan="2"> 24 </Td> <Td_colspan="1"> June 5, 2012 (2012 - 06 - 05) </Td> <Td> March 19, 2013 (2013 - 03 - 19) </Td> <Td> 2.59 </Td> <Td> 1.1 </Td> </Tr> <Tr> <Td> </Td> <Td_colspan="1"> </Td> <Td_colspan="2"> 24 </Td> <Td_colspan="1"> June 11, 2013 (2013 - 06 - 11) </Td> <Td> March 18, 2014 (2014 - 03 - 18) </Td> <Td> 2.53 </Td> <Td> 1.1 </Td> </Tr> <Tr> <Td> </Td> <Td_colspan="1"> 5 </Td> <Td_colspan="2"> 25 </Td> <Td_colspan="1"> June 10, 2014 (2014 - 06 - 10) </Td> <Td> March 24, 2015 (2015 - 03 - 24) </Td> <Td> 2.01 </Td> <Td> 0.9 </Td> </Tr> <Tr> <Td> </Td> <Td_colspan="1"> 6 </Td> <Td_colspan="2"> 20 </Td> <Td_colspan="1"> June 2, 2015 (2015 - 06 - 02) </Td> <Td> March 15, 2016 (2016 - 03 - 15) </Td> <Td> 1.72 </Td> <Td> 0.8 </Td> </Tr> <Tr> <Td> </Td> <Td_colspan="1"> 7 </Td> <Td_colspan="2"> 20 </Td> <Td_colspan="1"> June 21, 2016 (2016 - 06 - 21) </Td> <Td> June 27, 2017 (2017 - 06 - 27) </Td> <Td> 1.11 </Td> <Td> 0.6 </Td> </Tr> </Table>

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