World Map, colour-coded to show the years the countries started of the process of official conversion to the metric system. Using data from PhD thesis by Hector Vera<sup id="cite_ref-1" class="reference"><a href="#cite_note-1">[1]</a></sup> and NIST<sup id="cite_ref-2" class="reference"><a href="#cite_note-2">[2]</a></sup>. Magenta is preliminary 1795, and cyan is 1998; black is for countries having not adopted metric system yet, and grey is for countries with no data on their adoption year. The data used by this map can be viewed by pressing the "Edit" tab and viewing the underlying code. 
<div class="reflist" style="list-style-type: decimal;">
<ol class="references"><li id="cite_note-1"><span class="mw-cite-backlink"><a href="#cite_ref-1">↑</a></span> <span class="reference-text">Vera, Hector (2011-09) <cite>The Social Life of Measures: Metrication in the United States and Mexico, 1789–2004</cite> (PhD dissertation)<sup><a rel="nofollow" class="external autonumber" href="https://www.proquest.com/docview/924487292/3D7EDF35B314DCAPQ/1">[1]</a></sup>, Sociology and Historical Studies, New School for Social Research, pages 51, 494–497</span>
</li>
<li id="cite_note-2"><span class="mw-cite-backlink"><a href="#cite_ref-2">↑</a></span> <span class="reference-text"><cite class="book" style="font-style:normal">(20 May 1975) <i> <a rel="nofollow" class="external text" href="http://nvlpubs.nist.gov/nistpubs/Legacy/SP/nbsspecialpublication420.pdf">The International Bureau of Weights and Measures 1875–1975: NBS Special Publication 420</a></i>, <a href="https://en.wikipedia.org/wiki/Washington,_D.C." class="extiw" title="w:Washington, D.C.">Washington, D.C.</a>:  National Bureau of Standards, p. 244  <small></small></cite></span>
</li>
</ol></div>
Authors of <a href="//commons.wikimedia.org/wiki/File:BlankMap-World.svg" title="File:BlankMap-World.svg">BlankMap-World.svg</a>
<a href="//commons.wikimedia.org/wiki/File:BlankMap-World.svg" title="File:BlankMap-World.svg">BlankMap-World.svg</a> <i>by</i> various authors