I found a more detail history of the 12th....
12th Regiment, Wisconsin Infantry
Organized in Madison, Wis., October 18 to December 13, 1861. Left State for Fort Leavenworth, Kansas, January 11, 1862. At Weston, Mo., till February 15. Reach Fort Leavenworth February 16. Attached to Dept. of Kansas to June, 1862. District of Columbus, Ky., Dept. of the Tennessee, to October, 1862. 3rd Brigade, 4th Division, District of Jackson, Tenn., to November, 1862. 3rd Brigade, 4th Division, Right Wing 13th Army Corps (Old), Dept. of the Tennessee, to December, 1862. 3rd Brigade, 4th Division, 17th Army Corps, to January. 1863. 3rd Brigade, 4th Division, 16th Army Corps. to July, 1863. 3rd Brigade, 4th Division, 13th Army Corps, to August, 1863. 3rd Brigade, 4th Division, 17th Army Corps, to April, 1864. 1st Brigade, 4th Division, 17th Army Corps, to July. 1864. 1st Brigade, 3rd Division, 17th Army Corps, to July, 1865.
March from Fort Leavenworth to Fort Scott, Kansas, March 1-7, 1862, and duty there till March 27. Ordered to Lawrence, Kansas, March 27, thence to Fort Riley April 20 and to Fort Leavenworth May 27. Moved to St. Louis, Mo., thence to Columbus, Ky., May 29-June 2. Repairing Mobile & Ohio Railroad and duty at Union City and Humboldt, Tenn., till October 1. Moved to Bolivar October 1 and duty there till November 2. Grant's Central Mississippi Campaign, operations on the Mississippi Central Railroad, November 2, 1862, to January 10, 1863. Reconnoissance from La Grange toward Hilly Springs November 8, 1862. Moved to Lumpkin's Mills December 24, thence march to Colliersville, Tenn., via Holly Springs, Moscow and Lafayette, and guard duty along Memphis & Charleston Railroad till March 14, 1863. Moved to Memphis and duty there till May. Expedition to Coldwater River April 18-24. Hernando April 18. Perry's Ferry, Coldwater River, April 19. Ordered to Vicksburg, Miss., May 11. Siege of Vicksburg , Miss., May 22-July 4. Advance on Jackson, Miss., July 4-10. Siege of Jackson July 10-17. Duty at Vicksburg till August 15. Ordered to Natchez, Miss., August 15, and duty there till November 22. Expedition to Harrisonburg September 1-8. Near Harrisonburg and capture of Fort Beauregard September 4. Ordered to Vicksburg, Miss., November 22 and duty there till February, 1864. *******n Campaign February 3-March 2. Champion's Hill and Bolton's Depot February 4. Canton February 29. Veterans on furlough till May. Non-veterans on duty at Vicksburg till April, then join Regiment at Cairo, Ill. Moved to Clifton, Tenn., May 5-14, thence march to Ackworth, Ga., via Huntsville and Decatur, Ala., and Rome, Ga., May 14-June 8. Atlanta (Ga.) Campaign May 8 to September 8. Operations about Marietta and against Kenesaw Mountain June 10-July 2. Assault on Kenesaw June 27. Nickajack Creek July 2-5. Howell's Ferry July 5. Chattahoochie River July 5-17. Nickajack Creek July 6-8. Leggett's or Bald Hill July 20-21. Atlanta July 22. Siege of Atlanta July 22-August 25. FACE="Courier Ezra Chapel, July 28. Flank movement on Jonesboro August 25-30. Battle of Jonesboro , August 31-September 1. Lovejoy Station September 2-6. Operations against Hood in North Georgia and North Alabama September 30-November 3. March to the sea November 15-December 10. Siege of Savannah December 10-21. Campaign of the Carolinas January to April, 1865. Pocotaligo, S. C., January 14. Salkehatchie Swamp, February 2-5. Binnaker's Swamp, South Edisto River, February 9. Orangeburg February 11-12. Columbia February 16-17. Battle of Bentonville, N. C., March 19-21. Occupation of Goldsboro March 24. Advance on Raleigh April 10-14. Occupation of Raleigh April 14. Bennett's House April 26. Surrender of Johnston and his army. March to Washington, D. C., via Richmond, Va., April 29-May 19. Grand Review May 24. Moved to Louisville, Ky., June. Mustered out July 20, 1865.
Regiment lost during service 3 Officers and 93 Enlisted men killed and mortally wounded and 3 Officers and 224 Enlisted men by disease. Total
Here is a another history of the 100th....
100th Regiment, Indiana Infantry
Organized at Fort Wayne, Ind., and mustered in September 10, 1862. Left State for Memphis, Tenn., November 11. Attached to 2nd Brigade, District of Memphis, Tenn., 13th Army Corps (Old), Dept. of the Tennessee, November, 1862. 1st Brigade, 1st Division, District of Memphis, 13th Army Corps, to December, 1862. 1st Brigade, 1st Division, 17th Army Corps, to January, 1863. 1st Brigade, 1st Division, 16th Army Corps, to July, 1863. 1st Brigade, 4th Division, 15th Army Corps, to August, 1864. 2nd Brigade, 4th Division, 15th Army Corps, to September, 1864. 2nd Brigade, 1st Division, 15th Army Corps, to June, 1865.
SERVICE.- Grant's Central Mississippi Campaign. Operations on the Mississippi Central Railroad November 26, 1862, to January 10, 1863. Duty at Colliersville, Tenn., and along the Memphis & Charleston Railroad till June 7. Ordered to Vicksburg, Miss., June 7. Siege of Vicksburg June 14-July 4. Advance on Jackson, Miss., July 4-10. Siege of Jackson July 10-17. Camp at Big Black till September 28. Moved to Memphis, Tenn., thence march to Chattanooga, Tenn., September 28-November 20. Operations on the Memphis & Charleston Railroad in Alabama October 20-29. Chattanooga-Ringgold Campaign November 23-27. Tunnel Hill November 23-24. Mission Ridge November 25. March to relief of Knoxville, Tenn., November 28-December 8. Moved to Scottsboro, Ala., and duty there December 17, 1863, to May, 1864. Atlanta (Ga.) Campaign May 1 to September 8. Demonstration on Resaca May 8-13. Near Resaca May 13. Battle of Resaca May 14-15. Movement on Dallas May 18-25. Operations on line of Pumpkin Vine Creek and battles about Dallas, New Hope Church and Allatoona Hills May 25-June 5. Operations about Marietta and against Kenesaw Mountain June 10-July 2. Brushy Mountain June 15. Assault on Kenesaw June 27. Nickajack Creek July 2-5. Chattahoochie River July 5-17. Battle of Atlanta July 22. Siege of Atlanta July 22-August 25. Ezra Chapel, Hood's second sortie, July 28. Flank movement on Jonesboro August 25-30. Battle of Jonesboro August 31-September 1. Lovejoy Station September 2-6. Operations against Hood in North Georgia and North Alabama September 29-November 3. March to the sea November 15-December 10. Griswoldsville November 22. Siege of Savannah December 10-21. Campaign of the Carolinas January to April, 1865. Reconnoissance to Salkehatchie River, S. C., January 25, 1865. Congaree Creek, S. C., February 15. Columbia February 16-17. Battle of Bentonville, N. C., March 19-21. Mill Creek March 22. Occupation of Goldsboro March 24. Advance on Raleigh April 10-14. Occupation of Raleigh April 14. Bennett's House April 26. Surrender of Johnston and his army. March to Washington, D. C., via Richmond, Va., April 29-May 20. Grand Review May 24. Mustered out July 8, 1865. Recruits transferred to 48th Indiana Infantry.
Regiment lost during service 2 Officers and 56 Enlisted men killed and mortally wounded and 3 Officers and 173 Enlisted men by disease. Total 234.
I think this will answer your question of when they were near your town,,,,