Two troops of regular cavalry were armed with lances as an experiment in the 1840s but the idea didn't catch on. During the Mexican war, some members of the Mexican spy company carried lances and a few lancer militia units flourished before the civil war, the union bought 4,000 lances from contractors at the start of the CW most of them ended up surplus to requirements, only a handful of lancer regiments were raised and a few saw active service. The 1st Michigan Cavalry, who grandly called themselves the 1st United States Lancers, modelled themselves on the British 16th Lancers. The Michigan Lancers were fully equipped with lances as well as standard issue carbines, pistols and equipment, they were later disbanded because of the number of Canadians in their ranks, it was thought that if Britain entered the war on the side of the South against the Union, then the Canadians may well cause trouble out of loyalty to their mother country.
Robin Smith, American Civil War Union Army