Descriptive Catalogue of Wrought-Iron Bridges
- Facsimile of the company catalogue published around 1874.
- http://quod.lib.umich.edu/cgi/t/text/pageviewer-idx?c=moa;cc=moa;rgn=full%20text;idno=AJR3428.0001.001;didno=AJR3428.0001.001;view=image;seq=00000001

Keystone Bridge Co. v Phoenix Iron Co.
- Full text of case before the U.S. Supreme Court in 1877. Concerns the infringement of two patents belonging to the company.
- http://supreme.justia.com/us/95/274/case.html

Historic Bridges of the Midwest
- Photographic records of three bridges constructed by Keystone.
- http://bridges.midwestplaces.com/browse/by/builder/keystone/