John Neilson (ca. 1775–1827), master builder, was banished from his native Ireland under suspicion of involvement in the 1798 rebellion against British rule. He soon came to Philadelphia and worked there as a laborer and carpenter. TJ employed him at Monticello in 1804, thus beginning Neilson’s long working relationship with James Dinsmore. In April 1809 James Madison hired them to begin renovations at Montpellier, where Neilson remained until it neared completion in 1813. Two years later TJ unsuccessfully recommended him as “an honest, sober, and excellent” choice for public reconstruction work at Washington. Neilson and Dinsmore were working in Petersburg in 1817, when TJ hired them to work on the fledgling University of Virginia. Neilson was the master builder for Pavilions IX, X, and seven dormitories. He assisted Dinsmore on the design for the Rotunda and Anatomical Hall and executed numerous drawings and plans, most notably the drawing used in Peter Maverick’s 1822 and 1825 engravings of the layout of the university. Neilson worked from 1817 to 1820 at Bremo, John Hartwell Cocke’s Fluvanna County estate. He settled in Charlottesville, where he built several houses, including his own. At his death Neilson’s personal estate was valued at about $7,436, including eleven slaves and a sizable library. The proceeds from the estate went to his widow and other family members in northern Ireland (Lay, Architecture description begins K. Edward Lay, The Architecture of Jefferson Country: Charlottesville and Albemarle County, Virginia, 2000 description ends , 96, 97, 98–9; Richard R. Madden, The United Irishmen: Their Lives and Times, 2d ser. [1858], 1:336–8; Naturalization certificate, 28 Sept. 1804 [Philadelphia City Archives]; James Robinson, The Philadelphia Directory, City and County Register for 1802 [Philadelphia, 1802], 181; Robinson, The Philadelphia Directory for 1804 [Philadelphia, 1804], 170; Richard Charles Cote, “The Architectural Workmen of Thomas Jefferson in Virginia,” 2 vols. [Ph.D. diss., Boston University, 1986]; TJ to Madison, 19 Apr. 1809; TJ to Munroe, 4 Mar. 1815; TJ to Benjamin Henry Latrobe, 11 May 1815; Promissory Note from TJ to Neilson, 11 Apr. 1816; TJ to Dinsmore, 13 Apr. 1817; MB description begins James A. Bear Jr. and Lucia C. Stanton, eds., Jefferson’s Memorandum Books: Accounts, with Legal Records and Miscellany, 1767–1826, 1997, The Papers of Thomas Jefferson, Second Series description ends ; Articles of Agreement between Cocke, Dinsmore, and Neilson, 23 Dec. 1817 [ViU: Cocke Family Papers]; TJ to Arthur S. Brockenbrough, 12 Mar. 1823; Albemarle Co. Will Book, 9:205–6, 269–80).

On 10 Sept. 1812 Neilson obtained a similar testimonial from Madison, who described him as “unusually skilfull in his profession” and “very faithfull” in his work (Tr in DNA: RG 42, LRSCW, filed with TJ to Munroe, 4 Mar. 1815; printed in Madison, Papers description begins William T. Hutchinson, Robert A. Rutland, John C. A. Stagg, and others, eds., The Papers of James Madison, 1962– , 31 vols.  Congress. Ser., 17 vols.  Pres. Ser., 6 vols.  Sec. of State Ser., 8 vols description ends , Pres. Ser., 5:299).