This is a file from the Wikimedia Commons. Information from its description page there is shown below. Commons is a freely licensed media file repository. You can help.
English: Average annual number of employed coal miners in the United States, 1890-2014
Date
Source
Own work
Author
Plazak
Graph of data from two sources. 1900-2014 from US Department of Labor MSHA website:
http://arlweb.msha.gov/stats/centurystats/coalstats.asp
Data 1890-1900 from: Historical Statistics of the United States, US Department of Commerce, 1960, p.358-359.
Licensing
I, the copyright holder of this work, hereby publish it under the following license:
This file is licensed under the Creative Commons Attribution-Share Alike 4.0 International license.
You are free:
to share – to copy, distribute and transmit the work
to remix – to adapt the work
Under the following conditions:
attribution – You must give appropriate credit, provide a link to the license, and indicate if changes were made. You may do so in any reasonable manner, but not in any way that suggests the licensor endorses you or your use.
share alike – If you remix, transform, or build upon the material, you must distribute your contributions under the same or compatible license as the original.