While living in Chenango County, New York, David is listed as donating $3.00 to the New York Institution in 1827, undoubtedly in support of his brother John who was a deaf and dumb pupil there.⁷

As early as 1834, David was living in Nelson County, Kentucky, where he signed a petition sent to the U.S. Senate.⁸

On 8 September, 1838, while living in Jefferson County, Kentucky, David purchased eighty acres of land in Crawfordsville, Indiana, that were available from the sale of public lands. The property is described as “the North East quarter of the South East quarter and the South West quarter of the South East quarter of section three, in Township fifteen north, of Range Six West, in the District of lands subject to sale at Crawfordsville, Indiana, containing eighty acres.” It is unknown whether he ever lived on this land.⁹

David was a school teacher and principal during the establishment of the Louisville, Kentucky, public school system. The Legislature of Kentucky granted the first charter to the town of Louisville in 1828. In the month of March, 1829, John C. Bucklin, the first mayor of the city, recommended, in a message to the council, “the adoption of some well-digested system for establishing a permanent free school.” Mr. Manor Butler, a gentleman at the time widely known in the West as an able educator, was appointed principal teacher. For a period of five years the schools went on prosperously under the able superintendence of Mr. Butler. At the close of the school year, 1833-4, however, becoming dissatisfied with the Lancasterian Method of instruction, then very popular with the city authorities, Mr. Butler resigned his position as principal. David M. Gazlay, having recently arrived in Louisville from New York, succeeded Mr. Butler as principal and also had special charge of the Grammar School. During this same year, the Night School System was inaugurated in Louisville, which is credited with having the first night school and the first Superintendent of Schools in the United States. On October 22, 1834, a resolution was adopted ordering a night school to be opened on the first Monday in November and continue in session four months. This school was to be taught by the principals of the Grammar and Primary Departments of the city school, Mr. David M. Gazlay and Mr. Joseph Toy. Mr. Toy had been elected principal of the Primary Department of the city school in September. On February 21, 1835, Messrs. Gazlay and Toy made a report of the work of the night school for the session just closed. During the session, twenty-two boys had been in attendance studying reading, writing, and arithmetic. The night school was conducted for another four month session on 16 November 1835, with Mr. Gazlay as teacher. The session closed on March 12, 1836, with a total enrollment of twenty-four pupils. A majority of these were apprentices in the various shops in the city. With this session, the night school closed until 1842.^{10, 11}

David apparently continued teaching in Louisville to at least 1851, as suggested by advertisements in several grammar and spelling books for Mitchell’s American System of Standard School Geography. The advertisements include testimonials by various educators, such as one in 1848 by D. M. Gazlay: “I have partially examined Mitchell’s Geography and Atlas, and am convinced that it is superior to Woodbridge or Olney both in arrangement and correctness, and have introduced it into my school.”¹²

He is probably the D. M. Gazlay who is listed in the US tax assessment list, residing in Division No. 3 of Collection District No. 3 of the State of Kentucky, 27 June 1863, and so he was apparently still living in Louisville, Kentucky at the time.¹³

David is listed as Montross Gasley in the 1865 New York census, living with his sister Sarah (Gazlay) Warner and her husband Benjamin. This is the only known public record where he is listed as Montross, which is understood to be his middle name based on an unpublished family history. It seems likely that David moved with Sarah and Benjamin to the north-eastern corner of Connecticut (“the quiet corner”) soon after 1865, possibly to be near their daughter-in-law Angeline (Gleason) Warner since their son Addison had died the previous year in the Civil War, leaving Abigail to care for their three year old daughter Pamelia.²

He married Angeline (nee Gleason) Warner in Massachusetts in 1868 and settled in Pomfret, Connecticut, where he spent his remaining years in retirement.