Robert Sinclair (1772–1853), manufacturer, was a lifelong resident of Baltimore and a member of the Maryland Agricultural Society, the Maryland Society for Promoting the Culture of the Vine, and a local fire company. He established a factory to produce agricultural implements in Baltimore in 1820 and added a seed store shortly thereafter. This concern, which was called Sinclair & Moore from 1825, sold, among other things, Thomas Mann Randolph’s “Hill Side Ploughs.” It remained in operation until at least 1835 (J. Thomas Scharf, History of Baltimore City and County [1881], 930; Federal Intelligencer, and Baltimore Daily Gazette, 8 Sept. 1795; Federal Gazette & Baltimore Daily Advertiser, 4 Jan. 1812; Baltimore American Farmer, 3 Mar., 2 June, 29 Dec. 1820; DNA: RG 29, CS, Md., Baltimore, 1820–40; The Baltimore Directory, for 1822 & ’23 [Baltimore, 1822], 250; Baltimore Patriot & Mercantile Advertiser, 28 June 1822, 3 May 1823; Easton, Md., Republican Star and General Advertiser, 31 May 1825; Baltimore Gazette and Daily Advertiser, 23 Sept. 1828; Matchett’s Baltimore Director, Corrected up to September, 1835. For 1835–6 [1835]; Baltimore Sun, 28 Oct. 1853; gravestone inscription in Friends Cemetery, Baltimore).

Sinclair’s letter to TJ of the 8th, not found, is recorded in SJL as received 12 July 1822 from Baltimore.