1868 plat map of <a href="https://en.wikipedia.org/wiki/Helena,_Montana" class="extiw" title="w:Helena, Montana">Helena, Montana</a>, U.S.
<dl><dd>Uploader added light blue color fill to streets, that was not in the 1868 original.</dd></dl>
A. C. Wheaton, T. E. (apparently the 1868 equivalent of a civil engineer)
<ul><li>Connor, Glen (August 2006) "HISTORY OF WEATHER OBSERVATIONS HELENA, MONTANA". "Appendix 2: Wheaton's Helena Plat Map. "</li>
<li>Notation in source: "prepared for the Midwestern Regional Climate Center under the auspices of the Climate Database Modernization Program, NOAA's National Climatic Data Center, Asheville, North Carolina."</li>
<li><a rel="nofollow" class="external free" href="https://mrcc.illinois.edu/FORTS/histories/MT_Helena_Conner.pdf">https://mrcc.illinois.edu/FORTS/histories/MT_Helena_Conner.pdf</a></li>
<li>Archive thereof: <a rel="nofollow" class="external free" href="https://web.archive.org/web/20200731212041/https://mrcc.illinois.edu/FORTS/histories/MT_Helena_Conner.pdf">https://web.archive.org/web/20200731212041/https://mrcc.illinois.edu/FORTS/histories/MT_Helena_Conner.pdf</a></li></ul>