Jonas Horwitz (1783–1852), physician and educator, was born in Berlin. He arrived in the United States in 1810, petitioned for citizenship in 1812, and in the following year advertised an evening school in Philadelphia at which he taught Hebrew, Chaldee, and Arabic. Horwitz received a medical degree from the University of Pennsylvania in 1815 and practiced medicine in Lexington, Kentucky, in 1816, and at a dispensary for the poor in Philadelphia in 1818. He continued to teach Hebrew in various locations, including the environs of Washington, D.C., 1819–20, and Raleigh, North Carolina, in 1822. Horwitz unsuccessfully petitioned to teach languages at Central College and in 1821 visited TJ at Monticello. By 1827 he had settled permanently in Baltimore, where he established a medical practice. Horwitz joined a unit of volunteer soldiers as a surgeon during the Mexican-American War. In 1850 he owned real estate valued at $10,000 (Jacob Rader Marcus, United States Jewry 1776–1985 [1989], 1:360–2, 376; Horwitz’s naturalization records, 8 May 1812 [DNA: RG 21, NPEDP]; Philadelphia Democratic Press, 25 Oct. 1813; University of Pennsylvania Catalogue description begins Will J. Maxwell, comp., General Alumni Catalogue of the University of Pennsylvania, 1917 description ends , 575; Lexington, Ky., Western Monitor, 28 June 1816; Rules and Regulations of the Northern Dispensary. for the Medical Relief of the Poor [(Philadelphia, 1818)], 12; John Adems Paxton, The Philadelphia Directory and Register, for 1819 [Philadelphia, 1819]; Samuel L. Mitchill to TJ, 4 May 1819; Washington Daily National Intelligencer, 15, 20 Nov. 1819; Boston Daily Advertiser, 24 Nov. 1819; Alexandria Gazette & Daily Advertiser, 13, 17 Jan. 1820; TJ to Frederick W. Hatch, 9 Sept. 1821; Hatch to TJ, [received 10 Sept. 1821]; Raleigh Register and North-Carolina Gazette, 25 Oct. 1822; Eugene Fauntleroy Cordell, The Medical Annals of Maryland, 1799–1899 [1903], 443–4; Baltimore Patriot & Mercantile Advertiser, 28 Apr. 1830, 28 Mar. 1831; DNA: RG 29, CS, Md., Baltimore, 1830–50; Horwitz, A Defence of the Cosmogony of Moses [(1838)]; Matchett’s Baltimore Director [1831]: 187; [1851]: 133; Baltimore Sun, 1 July 1852).

Horwitz transferred the publishing rights to the project described in the enclosure to Dobson, who completed it (תורה נביאים וכתובים. Biblia Hebraica, 2 vols. [Philadelphia, 1814], with unpaginated note on publication history).

In a letter presumably given to TJ by Thomas cooper during his autumn 1818 visit to Monticello, Horwitz asked Cooper to recommend him for a professorship of Oriental literature at Central College if the school “is intended to have the same standing {if not superior}” as Harvard, Yale, and the College of New Jersey (later Princeton University), all of which have such teaching positions and whose faculty, as well as “almost all the Clergy, besides many other literary Characters in the Eastern, Middle, & Western states have received the benefits of my instruction” (Horwitz to Cooper, Philadelphia, 11 Sept. 1818 [RC in ViU: TJP; addressed: “Thomas Cooper M.D. &C.”; endorsed by TJ: “Horwitz J. to be Hebrew Professor”]).