In recognition of Illinois’ six regiments' service in the Mexican War, regimental numbers for infantry in the Civil War began at seven. * 7th Illinois Volunteer Infantry Regiment (3 Months) * 7th Illinois Volunteer Infantry Regiment (3 Years) * 8th Illinois Volunteer Infantry Regiment (3 Months) * 8th Illinois Volunteer Infantry Regiment (3 Years) * 9th Illinois Volunteer Infantry Regiment (3 Months) * 9th Illinois Volunteer Infantry Regiment (3 Years) * 9th Illinois Volunteer Mounted Infantry Regiment * 10th Illinois Volunteer Infantry Regiment (3 Month) * 10th Illinois Volunteer Infantry Regiment (3 Year) * 11th Illinois Volunteer Infantry Regiment (3 Month) * 11th Illinois Volunteer Infantry Regiment (3 Year) * 12th Illinois Volunteer Infant