[6] After promotion to first lieutenant, Collamer served as aide-de-camp to Brigadier General John French, commander of the militia's 2nd Brigade, 4th Division.

[11][12] French's unit left Orange County for upstate New York in September 1814 in response to warnings of an imminent British invasion from Canada.

[6] When the brigade was crossing Lake Champlain en route to Plattsburgh, Collamer was sent ahead in a boat to inform Vermont Militia commander Samuel Strong that French's troops were on their way.

[6] Strong informed Collamer that the Battle of Plattsburgh had taken place the day before, and the British had retreated, so French's troops returned home.

[13] Among the prospective attorneys who studied law under his supervision was Lyman Gibbons, who later served as a justice of the Alabama Supreme Court.

[14] Collamer also served in local offices, including Register of Probate, Windsor County State's Attorney, and member of the Vermont House of Representatives.

[35] When the Committee on Territories, chaired by Stephen A. Douglas, recommended passage of the Crittenden Amendment, which proposed resubmitting for popular vote the pro-slavery Lecompton Constitution for Kansas, Collamer and James R. Doolittle of Wisconsin refused to vote in favor but instead crafted a persuasive minority report explaining their opposition.

[36] Collamer also represented the minority view in June 1860, when the select committee chaired by James Murray Mason issued its report on John Brown's raid on Harper's Ferry.

[37] Mason argued that Brown's raid was the work of an organized abolitionist movement, which needed to be curtailed with federal authority.

[39] His colleagues were known to pay close attention to his remarks on the Senate floor even though he spoke infrequently and even then too quietly to reach the entire chamber or the galleries.

[41] At the 1860 Republican National Convention, Collamer received the favorite son votes of Vermont's delegates and withdrew after the first ballot.

[44] Collamer was the lead senator of the nine Republicans who visited Lincoln in 1862 to argue for change in the composition of his cabinet by persuading him to replace his Secretary of State, William Henry Seward.

[47] After the war, Collamer opposed the Reconstruction of plans of Presidents Lincoln and Andrew Johnson and was an advocate of Congressional control over the process of readmitting former Confederate states to the Union.

[50] In 1881, the state of Vermont donated a marble statue of Collamer created by Preston Powers to the U.S. Capitol's National Statuary Hall Collection.