The following is a summary of acts which authorized boundary changes for Union County.

1. Acts of 1855-56, Chapter 156, Section 2 transferred the lands of residence of Drury Laffoon into Claiborne County from Union County.
2. Private Acts of 1859-60, Chapter 196, Section 5 moved the farm belonging to William Albright from Campbell County into Union County; Section 6 moved the properties of John Robertson, Howard M. Hubbs, and William H. Dyer from Knox County into Union County but did not relieve these families from paying the railroad tax levied in Knox County; Section 8 changed the boundary lines between Union and Campbell counties so as to cause to leave in Campbell County John Lay's bend of the Powell River leaving Powell's River at the narrows of said bend and below William Swint's and running across said narrows to Powell's River at the lower end of John Lay's farm.
3. Public Acts of 1867-68, Chapter 60, Section 13, changed the lines between Union and Claiborne counties so as to include the farm and dwelling of Silas Williams in Union County.
4. Public Acts of 1870-71, Chapter 118 changed the lines between Union and Grainger counties so as to include all the properties of James Dyer, Senior, and James Dyer, Junior, in Union County.
5. Public Acts of 1871, Chapter 7, altered the lines between Campbell County and Union County so as to place all the farms and residences of John S. Spangler and John K. Farris in Union County.
6. Public Acts of 1873, Chapter 72, transferred all the farm of James McHaffee from Union into Knox County, said McHaffie having filed a petition seeking the same, and provided that such action would not reduce Union County below the constitutional limitation on square miles and would not place the county line nearer than eleven miles to the courthouse of Union County.
7. Public Acts of 1873, Chapter 77, created the new county of Webster from parts of
   Claiborne, Campbell, and Union counties.
8. Public Acts of 1875, Chapter 140, Section 4, changed the boundary line between Union and Knox counties so as to place all the lands of John Anderson and W. Edward Anderson out of Knox County and into Union County.
9. Public Acts of 1879, Chapter 111, changed the boundary line between Union and Claiborne counties so as to place the entire farm of Benjamin Pike into Claiborne County from Union County.
10. Public Acts of 1879, Chapter 137, Section 12, changed the boundary line between Union and Claiborne counties so as to include the farms of Issac Holoway, John D. Parker and Jacob Leach in Claiborne County.
11. Public Acts of 1883, Chapter 40, took all the properties of Andrew Pary, Richard Pary, Mary McBee, Jasper Woods, John Houston, William Shofner, Henry Keck, and William Blason which were in Union County and placed them in Claiborne County.
12. Public Acts of 1883, Chapter 103, provided that the tract of land owned by Joseph McHaffee be transferred from Knox County into Union County.
13. Public Acts of 1883, Chapter 129, changed the boundary line between the counties of Union and Grainger from Log Mountain in Grainger County to the Clinch River in Union County. This act was repealed by Public Acts of 1890, Second Extra Session, Chapter 5, except that the properties of V. W. Capps remained in Grainger County. Otherwise the boundary lines reverted to their statues before the passage of that 1883 act.
14. Public Acts of 1887, Chapter 45, moved all the lands of Benjamin Pike from Union County into Claiborne County.
15. Public Acts of 1887, Chapter 47, changed the lines between Union and Knox counties so that all the property of Calvin Kitts be included in Union County.
16. Public Acts of 1887, Chapter 49, transferred the lands of J. T. Inklebarger from Union County into Grainger County. This act was repealed by Public Acts of 1895, Chapter 188. However, Private Acts of 1901, Chapter 361 repealed Public Acts of 1895, Chapter 188, so as to transfer the lands of J. T. Inklebarger from Union County into Grainger County.
17. Public Acts of 1887, Chapter 227, moved the farms belonging to Harvey Williamson, Berry Ellison and Josiah Smith into Union County from Claiborne County.
18. Public Acts of 1889, Chapter 24, changed the boundary line between Union and Grainger counties so as to include the lands of G. W. Hollingsworth, William Hollingsworth, B. M. McPhetridge and B. Shelton in Grainger County.
19. Public Acts of 1889, Chapter 194, changed the lines between Knox and Union counties so that all the properties of Charles H. Smith, R. H. Harless, A. K. Mynatt, L. D. Bates and Joseph Bates be included in Knox County.
20. Public Acts of 1891, Chapter 53, changed the boundary line between the counties of Union and Claiborne so as to include the farms of Andrew Pary, Richard Pary, Mary McBee, Jasper Wood, John Houston, William Schoffner, Henry Keck, Jr., and William Beeson in Union County.
21. Public Acts of 1891, Chapter 255, transferred the lands of Alvin Brogans and Frankley Collin's from Union County into Claiborne County.
22. Public Acts of 1895, Chapter 7, changed the boundary line between Union and Claiborne counties so as to move the farms and residences of John Woods, Lida Broguns, William Bullard, Isaac and Hiram Schoffner from Claiborne County into Union County and the land of R. P. Rucher and T. N. Cheatham from Union County into Claiborne County.
23. Public Acts of 1895, Chapter 104, detached the farm of V. W. Capps from Grainger County and attached the same to Union County.
24. Public Acts of 1895, Chapter 183, moved all that portion of the Samuel Bayless farm lying north of the Raccoon Valley Road from Knox County into Union County.
25. Public Acts of 1895, Chapter 215, transferred the properties of J. J. Woods, W. J. Woods, and S. C. Woods from Claiborne County into Union County and the farms of Marharet E. Cheatham, W. A. Cheatham, and John Rollins from Union into Claiborne County.
26. Public Acts of 1899, Chapter 233, changed the lines between Union and Grainger counties so as to include all the land belonging to J. A. Popejoy and E. E. Dyer in Union County. This act was repealed by Private Acts of 1901, Chapter 310.
27. Acts of 1903, Chapter 386, changed the boundary line between Union and Campbell counties by so that fifty acres described as follows: on the north by the Thomas farm, south and west by the Craig farm; on the east by the Lindamond farm, be placed in the second civil district of Campbell County.
28. Acts of 1905, Chapter 68, changed the boundary line between Union and Claiborne counties so as to place all the lands belonging to J. M. Whited out of Claiborne County and put them into Union County.
29. Acts of 1905, Chapter 71, changed the boundary line between Union and Grainger counties so as to place the lands of J. T. Inklebarger into Grainger County from Union County.
30. Acts of 1905, Chapter 186, changed the boundary line between Union and Knox counties so as to transfer a small triangular shaped piece of land belonging to W. E. Smith and William Childress from Knox County into Union County.
31. Acts of 1907, Chapter 394, transferred the farm of F. M. Williams from Claiborne County into Union County.
32. Acts of 1909, Chapter 68, changed the boundary line between Union and Knox counties so as to include the Hugh Caldwell farm in Union County.
33. Private Acts of 1919, Chapter 393 changed the boundary line between Union and Claiborne County line so as to include in Claiborne County all the farm of William Russell which adjoined the lands of William Ford, Jim Medley, and Jess Smith which now lies on both sides of the line, and to transfer all the property of G. S. Steiner whose lands adjoin Leach and Wilson into Union County.
34. Private Acts of 1919, Chapter 394, detached the farms of C. M. Cabbage, Lafayette Hamilton, and Jess Rush from Grainger County and attached the same to Union County.
35. Private Acts of 1937, Chapter 175 moved the lands of Mrs. J. M. Keck from the second civil district of Claiborne County into the seventh civil district of Union County.
36. Private Acts of 1947, Chapter 441 detached property of E. B. Shelby from the third civil district of Claiborne County and attached it to the sixth civil district of Union County.
37. Private Acts of 1963, Chapter 120, changed the boundary line between Knox and Union counties so as to include the farm of Clint Davis which was located in the sixth civil district of Knox County and placed it in the first civil district of Union County.