Lincolnshire is a county with a long history of human settlement and activity dating back to the Paleolithic (Old Stone Age) some 35000 to 200000 years ago. These mobile bands of early hunter-gatherers left little trace of their activity, although a few flint hand axes have been recovered. Many more finds of flint microliths have come from the Mesolithic (Middle Stone Age), mainly from upland limestone areas that may have been used as seasonal camp sites but still very little evidence of settlement or funerary rights has survived. With the coming of the Neolithic (New Stone Age) around 6000 years ago there was an influx of ideas from Europe possibly brought by traders that included agriculture as well as new forms of belief systems, particularly 'the cult of the ancestor'. This veneration of the dead was demonstrated by the building of huge earthen and chalk mortuary structures known as long barrows. An excavation of one of the Giant's Hills barrows by C. W. Phillips in 1933-4 revealed much information about the construction of the mound, and it is assumed that other long barrows may well have followed the same method of construction, although this cannot be certain as most remain unexcavated or badly damaged. Giant's Hills also illustrates many of the same features of size and location as the other surviving barrows - it was 65 metres long, 23 metres wide and was built near the top of a hillside overlooking a valley, its long axis following the contours of the landscape. It seems that the Lincolnshire barrows sizes, shapes and methods of construction are almost unique to this area, they range from between 24 metres to 78 metres in length, between 12 metres and 24 metres in width and seem to have been surrounded by a fully enclosing ditch structure.
Today the remaining barrows generally stand on the fringes of the chalk uplands known as the Lincolnshire Wolds. This is a range of hills that form a northwest to southeast spine along the eastern side of the county, measuring some 43 miles (70 km) long by 9 miles (15 km) wide and reaching a height of around 160 metres above sea-level. The actual number of these long barrows is open to dispute, I have shown the 12 known or probable sites on the map above (shown as large dark green clickable markers), the accompanying text mentions a further two which have now been destroyed by ploughing, while two others are open to question as to their age and purpose.
Due to the fact that Lincolnshire is one of the most intensively cultivated areas of the country it is unsurprising that so few of these barrows remain - many have undoubtedly been lost to the plough. Recent results of a survey by the Royal Commission on the Historical Monuments of England (RCHME) published by Dilwyn Jones have revealed over 50 cropmark enclosures (shown as small circular light green markers above) - possible examples of destroyed long barrows. It is not certain of course whether these enclosures were all barrows, it is possible that some were mortuary structures for which a mound was never built, one may be a minor cursus, others may be simply 18th century man-made rabbit warrens - it is unknown when, or if, many of these sites will ever be fully examined.
It is worth noting that while stone was used in the construction of monuments such a chambered tombs and stone circles during the Neolithic and Bronze Age in other parts of the country there is no evidence of these monuments ever being built in Lincolnshire.

List of remaining long barrows-
Ash Hill  On private land on part of the Swinhope estate north of Binbrook
Ash Holt  In a small wood east of Cuxwold
Beacon Plantation  In a small wood next to the A16 northwest of Swaby
Burgh on Bain  On farmland southwest of Burgh on Bain
Deadmen's Graves I, II  On farmland northwest of Claxby St. Andrew
Giant's Hills  On farmland north of Skendleby (page includes the destroyed Giant's Hills II)
Hills Brough Farm  Probable barrow on private land south of Caistor
Hoe Hill I  On farmland north of Binbrook (page includes the destroyed Hoe Hill II)
Spellow Hills  On farmalnd southwest of Ulceby Cross
Tathwell  On farmland southwest of Tathwell
Thorganby  On private land on the Thorganby Hall estate