Please see the link below for a roster of units in being or raised for the war.
I know there were several Missouri regiments raised in the call of General Gaines early in the war but not many made it to the front. I think the 1st Missouri and the 2nd Missouri you mention were in that number.
There was only one Massachusetts Regiment called up for the war.
Most of the early campaigns in 1846 commanded by Taylor involved regulars as the major US force, but there were many volunteer regiments that campaigned with Scott on his way to Mexico City. There are plenty of accounts of their actions.
Doniphan's campaign and Wool's expedition were almost entirely made up of volunteers so look for accounts of these actions. Also see accounts of Buena Vista where most all units were volunteer.
Also, there were some US regiments raised for the war only (9 through 16th Infantry, the Voltiguers and Foot Riflemen and 3rd Dragoons). These outfits were not a force in being and essentially were made up of volunteers, not long service regulars.
Amazon.com has many Mexican War offerings. You may also want to see back issues of "Mexican War Journal" published by Descendants of Mexican War Veterans www.DMWV.org
James B. Ronan II
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