In earlier times the townland was probably uninhabited as it consists mainly of bog and poor clay soils. It was not seized by the English during the Plantation of Ulster in 1610 or in the Cromwellian Settlement of the 1660s so some dispossessed Irish families moved there and began to clear and farm the land. The 1790 Cavan Carvaghs list spells the name as
Tullynegross. The Tithe Applotment Books for 1826 list eleven tithepayers in the townland. The 1836 Ordnance survey Name books state-
There is an ancient fort near the north side and a small lake on the north boundary. It is bounded by a large stream or river on the west and south sides. The Tullynacross Valuation Office Field books are available for August 1839.
Griffith's Valuation of 1857 lists nine landholders in the townland. The landlord of Tullynacross in the 19th century was Leonard Dobbin. ==Census==