L.N. Engelgardt was born in 1766 in the estate of his father in Smolenskaya province, which was presented to him by the king of Poland Sigizmund. Being 11 years old the boy officially entered military service as a sergeant in the garrison of Vitebsk, and later in the Preobrazhensky regiment in St. Petersburg. In 1783 he was appointed an aide-de-camp to Prince Potemkin who was his father's cousin.
During the Russian-Turkish war of 1784-1790 Engelgardt fought under command of the field marshal Rumyantsev-Zadunaisky and in 1794 - under command of A.V. Suvorov.
In 1806 the gentry of Kazan has elected Engelgardt commander of the newly established militia. For his accomplishments in that area he was awarded the Order of St. Anne. In 1799 Engelgardt married Catherine Tatischeva, a daughter of a Moscow merchant who was known as a Mason. They had four children: Peter, Anastasia, Natalia and Sophia. In winter of 1826 Yevgeny Boratynsky got acquainted with Engelgardt's family and soon he married Engelgardt's elder daughter. The younger daughter later became the wife of N.V. Putyata.
In the 1820s the Engelgardts lived in Moscow in their own house on Nikitskaya street. In 1826 Boratynsky became their neighbor.
Both the Engelgardts and the Boratynsky spent summers in the estate Muranovo near Moscow that was bought by Catherine Engelgardt in 1816. There they lived in a single-storey building located in the southeastern corner of the estate. After the death of his father-in-law Boratynsky has built a new house of two storeys and has set a garden. Since the Engelgardts have settled in Muranovo it became a family estate that united the four noble families - the Engelgardts, the Boratynsky, the Putyata and the Tyutchevs.
In 1826 L.N. Engelgardt began the writing of his historical memoirs, which he dictated to his children in Muranovo. The work was finished a year before Engelgardt's death on November 4, 1836. In the memoirs Engelgardt tells about historical events and battles of the time of Catherine II, Paul I and Alexander I. N.V. Putyata published the book with his preface in the magazine "Russky vestnik" ("The Russian Gerald") and in 1867 P.Bartenev published it separately. Partly "The memoirs" were published in a collection "The Russian Memoirs. The Selected Pages. The18th century." (Moscow, 1988). The full publication of the book was carried out by the "Novoe Literaturnoe Obozrenije" in 1997.