Mashalisk was a Pocumtuck sonksqua (female sachem) who lived on the east side of Pemawatchuwatunck, the “long twisting mountain” now called the Pocumtuck Range, near the Connecticut River in present-day Deerfield, Massachusetts.

Each tribal community in the region had multiple male and female sachems (at least 35 at Sokoki (Northfield and Brattleboro, Vermont today), for example). Apart from the individuals who appear in colonial records and account books, most of their names are unknown. Like the sachem Umpanchela from Nonotuck (Northampton, Hadley, and Hatfield today), Mashalisk entered into a regular trading relationship with English fur traders and land brokers William and John Pynchon. Native people came to the truck house run by the Pynchons to exchange beaver furs and maize (corn) for English cloth, needles, ready-made wool coats, wampum, and sundry other trade goods. Mashalisk purchased multiple coats, which were likely given as gifts to her kinfolk.

In August 1672, and in April 1674, Mashalisk put her mark on deeds, orchestrated by John Pynchon and witnessed by her kinsman Ackambowet, that secured land on both sides of the Connecticut River, in the present-day towns of Deerfield, Leverett, Montague, Sunderland, and Wendell. The deed transacted in 1674 also settled the trading debts of her son, Wattawaluncksin. Mashalisk received valuable trade goods (wampum and wool coats) upon signing these documents, but there was no indication that she intended to relocate. The detailed descriptions of the landscape – along with clauses in other deeds indicating that Native people retained rights to hunt, fish, and set up wigwams on lands supposedly “sold” to Pynchon – suggest that these transactions may have been regarded, by Native signatories, as acknowledgements of their presence and continuing residence in the territory, more than as strict quit-claims.