Nineteen men, women, and children participating in a strike are killed in the <a href="https://en.wikipedia.org/wiki/Ludlow_Massacre" id="mwnA" rel="mw:WikiLink" title="Ludlow Massacre">Ludlow Massacre</a> during the <a href="https://en.wikipedia.org/wiki/Colorado_Coalfield_War" id="mwnQ" rel="mw:WikiLink" title="Colorado Coalfield War">Colorado Coalfield War</a>.<sup about="#mwt55" class="mw-ref reference" data-mw='{"name":"ref","attrs":{},"body":{"id":"mw-reference-text-cite_note-9"}}' id="cite_ref-9" rel="dc:references" typeof="mw:Extension/ref"><a href="./April_20#cite_note-9" id="mwng" style="counter-reset: mw-Ref 9;"><span class="mw-reflink-text" id="mwnw">[9]</span></a></sup>
<span class="mw-reference-text" id="mw-reference-text-cite_note-9"><cite about="#mwt52" class="citation book cs1" id="CITEREFRees2013">Rees, Jonathan (2013). "Ludlow Massacre". In Dubofsky, Melvyn (ed.). <a class="external text" href="https://books.google.com/books?id=D-NMAgAAQBAJ" id="mwBcE" rel="mw:ExtLink nofollow"><i id="mwBcI">The Oxford Encyclopedia of American Business, Labor, and Economic History. Volume 1: Abra to Mutu</i></a>. Oxford, UK: Oxford University Press. pp.<span id="mwBcM" typeof="mw:Entity"> </span>483–484. <a class="mw-redirect" href="./ISBN_(identifier)" id="mwBcQ" rel="mw:WikiLink" title="ISBN (identifier)">ISBN</a><span id="mwBcU" typeof="mw:Entity"> </span><a href="./Special:BookSources/978-0-19-999304-8" id="mwBcY" rel="mw:WikiLink" title="Special:BookSources/978-0-19-999304-8"><bdi id="mwBcc">978-0-19-999304-8</bdi></a>.</cite><span about="#mwt52" class="Z3988" id="mwBcg" title="ctx_ver=Z39.88-2004&amp;rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&amp;rft.genre=bookitem&amp;rft.atitle=Ludlow+Massacre&amp;rft.btitle=The+Oxford+Encyclopedia+of+American+Business%2C+Labor%2C+and+Economic+History.+Volume+1%3A+Abra+to+Mutu&amp;rft.place=Oxford%2C+UK&amp;rft.pages=483-484&amp;rft.pub=Oxford+University+Press&amp;rft.date=2013&amp;rft.isbn=978-0-19-999304-8&amp;rft.aulast=Rees&amp;rft.aufirst=Jonathan&amp;rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3DD-NMAgAAQBAJ&amp;rfr_id=info%3Asid%2Fen.wikipedia.org%3AApril+20"></span></span>