Lancashire at the time of the taking of the Domesday Survey in 1086, did not exist as a county. The area in the Domesday survey covered only the southern part of what is now Lancashire. The area extended from the northern shore of the River Mersey north to the River Ribble, the "terra inter Ripam et Mersham". It was almost wholly the domain of Count Roger of Poitou, third son of the great Earl Roger de Montgomery II, the seignor of Mont Gomerii in the arrondisement of Lisieux in Normandy. Roger of Poitou (sometimes Pictavencis, or in the West Riding as Roger le Poitevin) was given this land in recognition of the help his father gave to William in the conquest of Britain. He also had extensive and rich holdings in the West Riding of Yorkshire; grants were made by Duke William of Normandy in reward for his father, Roger de Montgomery's assistance at the Battle of Hastings.

Roger de Montgomery II was in command of a wing at the Battle of Hastings, but returned to Normandy with Queen Matilda, and the young Duke Robert. He was head of the council that governed the Duchy of Normandy in Duke William's absence. The family ancestry was closely entwined either by blood or marriage with the Duchy of Normandy. Roger de Montgomery had four sons. Eldest was Robert, Count of Alencon, and his successor. Followed by Hugh, Earl of Arundel and Shrewsbury, probably the main custodian of the family domains granted in England. Next youngest was Count Roger de Piotou who was made the first Earl of Lancaster by Duke William of Normandy. Philip, the youngest, accompanied Duke Robert on the first crusade to the Holy land and died there.

Lancashire was not a rich county. Coastal marsh stretched eastward to the forest which extended to the Penines. It was administered militarily by Hugh Lupus, the great Earl of Chester who also held most of the northern coast of Wales and both sides of the Dee and the Wirral. During the Baron's rebellion in 1069/70, Duke William of Normandy and his army of 40,000 men harried parts of Cheshire, most of Lancashire, and north to the Scottish border, the East and West Ridings of Yorkshire), Cumberland, and Northumberland. The land was left waste, most buildings having been reduced to rubble. Habitation was spotty and not well recorded in the Domesda Book. However, Roger de Poitou seems to have survived, probably because of his father's influence, although his holdings were considerably reduced by the time of the taking of the Domesday Survey in 1086. In 1081 he lost two important Lancashire lordships, Crosby and Warrington to the Norman Villers family, ancestors of the Traffords. He still retained as an under-tenant, some 45 coastal holdings from West Derby north to the Ribble, generally known as the Argarmeles.

Most of the land north of the Ribble, north to Heysham, was now held directly by the King. Most of this land, north of the Ribble, including Preston, Ribchester and Lancaster, was classified as being in Yorkshire, and was administered by Earl Tosti, under-tenant of the King. Little is known of Tosti. He may have been recruited from Normandy after the 1070 rebellion, but does not appear to be related to the notable Norman Tosni family. It was not until 1182 that Lancashire became a county, and these lands were included in Lancashire.

Meanwhile, at the time of the Domesday Book in 1086, Manchester was held by St.Mary's Church, Salford by Roger de Poitou. Liverpool was not then a village. However, many of the villages which now constitute parts of Liverpool did exist, including Allerton, Childwall, Bootle, Knowsley, Newsham, Huyton, Kirby, Kirkdale, Sefton, Speke, Up and Down Litherland, Roby, Toxteth, Walton on the Hill, Wavertree, West Derby, Woolton (all Roger de Poitou), and Smithdown (unknown).

Most of the coastal area north to the Ribble was also held by Roger de Poitou including Formby, Crosby, Thornton, Lydiate, Altcar, Maghull, Ince Blundell, Melling, Ainsdale, Southport(Erengermeles), North Meols and Argarmeles (Birkdale). Inland, Roger de Poitou held Blackburn, Dalton, Cockerham, Hurlston, Leyland, Penwortham, Newton le Willows, Rochdale, Skelmerdale, Up and Down Holland, and Preston(part).

Habitation and settlements in south central Lancashire were sparse unless they were ignored by the Domesday as having been wasted by Duke William in 1070 or later. The kink held most of the rest of southern Lancashire, and almost all of (what is now) northern Lancashire, including Heysham, Furness, Bardsea, Bispham, Marton (now Blackpool), Warton (Carnforth) and Lytham. The population of Lancashire (south of the Ribble) at the Domesday Book was probably less than 2,000 and mostly confined to the coastal area within 20 miles of the Irish Sea except for Warrington, Salford and Manchester.

North of the Ribble in the hundred known as Amounderness there were over 60 holdings and it was slightly more heavily populated but 45 settlements were waste, and held by Roger de Poitou.

Cheshire, to the south, was comparatively heavily populated and rich in holdings. The fate of Roger de Poitou is unknown although it is believed he returned to Normandy where Ansfrid de Montgommerio (successor to Roger de Montgommery II) witnessed a charter of Count Roger de Poitou in 1094. At this time he was giving to his local Abbey of St.Martin, a customary act of atonement by Norman magnates at the end of their careers and lives, which by many might have been called ruthless and despotic. Most of his holdings in Lancashire, those waste and those of value, were retaken by the King during or soon after the Domesday Book.

Notably absent from the Domesday Book were Liverpool, Ormskirk, Burnley and Oldham.