<P> Eighty - eight episodes were produced during the first four seasons; due to the 2007--2008 Writers Guild of America strike, the fifth season consisted of only 18 episodes . </P> <P> Over the course of nine seasons, One Tree Hill aired a total of 187 episodes . </P> <Table> <Tr> <Th_colspan="2"> Season </Th> <Th_colspan="2"> Episodes </Th> <Th_colspan="3"> Originally aired </Th> <Th_colspan="2"> Nielsen ratings </Th> </Tr> <Tr> <Th> First aired </Th> <Th> Last aired </Th> <Th> Network </Th> <Th> Rank </Th> <Th> Average viewership (in millions) </Th> </Tr> <Tr> <Td> </Td> <Td_colspan="1"> </Td> <Td_colspan="2"> 22 </Td> <Td_colspan="1"> September 23, 2003 (2003 - 09 - 23) </Td> <Td> May 11, 2004 (2004 - 05 - 11) </Td> <Td> The WB </Td> <Td> TBA </Td> <Td> 3.5 </Td> </Tr> <Tr> <Td> </Td> <Td_colspan="1"> </Td> <Td_colspan="2"> 23 </Td> <Td_colspan="1"> September 21, 2004 (2004 - 09 - 21) </Td> <Td> May 24, 2005 (2005 - 05 - 24) </Td> <Td> 117 </Td> <Td> 4.3 </Td> </Tr> <Tr> <Td> </Td> <Td_colspan="1"> </Td> <Td_colspan="2"> 22 </Td> <Td_colspan="1"> October 5, 2005 (2005 - 10 - 05) </Td> <Td> May 3, 2006 (2006 - 05 - 03) </Td> <Td> 139 </Td> <Td> 2.8 </Td> </Tr> <Tr> <Td> </Td> <Td_colspan="1"> </Td> <Td_colspan="2"> 21 </Td> <Td_colspan="1"> September 27, 2006 (2006 - 09 - 27) </Td> <Td> June 13, 2007 (2007 - 06 - 13) </Td> <Td> The CW </Td> <Td> 136 </Td> <Td> 2.9 </Td> </Tr> <Tr> <Td> </Td> <Td_colspan="1"> 5 </Td> <Td_colspan="2"> 18 </Td> <Td_colspan="1"> January 8, 2008 (2008 - 01 - 08) </Td> <Td> May 19, 2008 (2008 - 05 - 19) </Td> <Td> 184 </Td> <Td> 3.0 </Td> </Tr> <Tr> <Td> </Td> <Td_colspan="1"> 6 </Td> <Td_colspan="2"> 24 </Td> <Td_colspan="1"> September 1, 2008 (2008 - 09 - 01) </Td> <Td> May 18, 2009 (2009 - 05 - 18) </Td> <Td> 170 </Td> <Td> 2.8 </Td> </Tr> <Tr> <Td> </Td> <Td_colspan="1"> 7 </Td> <Td_colspan="2"> 22 </Td> <Td_colspan="1"> September 14, 2009 (2009 - 09 - 14) </Td> <Td> May 17, 2010 (2010 - 05 - 17) </Td> <Td> 130 </Td> <Td> 2.3 </Td> </Tr> <Tr> <Td> </Td> <Td_colspan="1"> 8 </Td> <Td_colspan="2"> 22 </Td> <Td_colspan="1"> September 14, 2010 (2010 - 09 - 14) </Td> <Td> May 17, 2011 (2011 - 05 - 17) </Td> <Td> 138 </Td> <Td> 1.8 </Td> </Tr> <Tr> <Td> </Td> <Td_colspan="1"> 9 </Td> <Td_colspan="2"> 13 </Td> <Td_colspan="1"> January 11, 2012 (2012 - 01 - 11) </Td> <Td> April 4, 2012 (2012 - 04 - 04) </Td> <Td> 180 </Td> <Td> 1.9 </Td> </Tr> </Table> <Tr> <Th_colspan="2"> Season </Th> <Th_colspan="2"> Episodes </Th> <Th_colspan="3"> Originally aired </Th> <Th_colspan="2"> Nielsen ratings </Th> </Tr>

When was the last episode of one tree hill aired