However, the year of his birth is uncertain. It is estimated as between 1697 and 1700, as in 1714 he was sent by Peter the Great to France to master the science of navigation. He remained there for much of the twenty years that followed. In 1729, Saltykov bought the estate of Marfino, and in 1731 he married Princess Praskovia Yuriyevna Trubetskaya, a daughter of Prince Yuri Yuriyevich Troubetzkoy by his first wife Princess Yelena Grigoriyevna Cherkasskaya, and on 19 January 1732 or 1733 his father was created a Count. In 1759, during the Seven Years' War of 1756-1763, he was appointed commander-in-chief of the Russian army and would soon win a victory at Palzig and Kunersdorf. In 1763, Saltykov became commander-in-chief of Moscow and was put in charge of the Moscow Senate Office. During Saltykov's time in office, he established a number of new post offices, restored Golovinsky and Kolomensky Palaces, and a number of city gates. They also repaired most of the worn-out bridges across the Moscow River and continued dismantling the walls of the White City in order to provide building material for the construction of the OrphanageВоспитательный дом ordered by Catherine the Great and the restoration of the Arsenal. In April 1764, Saltykov reported to Saint Petersburg on the opening of the Moscow Orphanage. With the purpose of providing Muscovites with food, Saltykov banned the removal of imported bread from the city and arranged for wholesale purchases of bread from landowners. He also secured regular wine deliveries to Moscow, the need for which had been estimated at 575,000 vedros. Saltykov was also fighting against gambling. In 1765, he took part in burning of books "harmful to the society" at the order of Empress Catherine II. During the plague outbreak in 1771, which caused mass departure of landowners, city officials, and rich merchants from Moscow, Pyotr Saltykov asked Catherine the Great for permission to leave the city. Without waiting for her reply, he left for his Marfino estate on the outskirts of Moscow. After a plague riot had broken out in Moscow on 16 September, Saltykov returned to the city. However, Catherine the Great relieved him of his post on 13 November 1771. A year later, he died on his estate at Marfino.
Family
By his wife Princess Praskovia Yuriyevna Trubetskaya, Saltykov had:
Countess Anastasia Petrovna Saltykova, married Pjotr Kwaschnin-Samarin
Countess Warwara Petrovna Saltykova, married on 4 November 1754 as his first wife Prince Wassili Borisovich Galitzine, later remarried, without issue from any of his marriages
