The Annexation Bill of 1866.

 "The Annexation Bill of 1866 was a bill introduced on July 2, 1866, but never passed in the United States House of Representatives. It called for the annexation of British North America and the admission of its provinces as states and territories in the Union. The bill was sent to committee but never came back, was never voted upon, and did not become law. The bill never came to the United States Senate." (Wikipedia).

References: Fred H. Harrington Fighting Politician: Major General N.P. Banks (Philadelphia, 1948). pp 178-179.

Donald Frederic Warner: The Idea of Continental Union: Agitation for the Annexation of Canada to the United States, 1849-1893. University of Kentucky Press 1960.

(The Canadian Pacific Railway was built from 1881 until 1885, partly in response to threats to annex Canada.)