Essex

"A county in the east of England, lying on the German Ocean, bounded by Suffolk, Cambridge, Hartfordshire and Middlesex; and separated by the Thames from Kent. It is about 54 miles long, and 48 broad, and is divided into 18 hundreds. Its surface is level, yet sufficiently varied not to be monotonous; but, excepting at a few points, the coast is flat and marshy. The rivers are the Thames, the Stour, the Lea, the Chelmer, the Blackwater, and the Coln. The soil is varied, but on the whole it is an admirable corn county. It has also excellent pastures; and some woods of considerable extent, such as Epping Forest. It produces in addition to farm produce, oysters called natives, and some few textile manufactures. Chelmsford is its county town, Colchester is a place of some importance." [Barclays Complete & Universal English Dictionary, 1842-1852]

"ESSEX, a county (maritime), bounded on the north by the counties of Suffolk and Cambridge; on the west by those of Hertford and Middlesex; on the south by the river Thames, which separates it from Kent; and on the east by the German ocean: it extends from 51° 30 to 52° 7 (N. Lat.), and from 0° 3 to 1° 1 (E. Lon.), and includes one thousand five hundred; and thirty-two square miles, or nine hundred and eighty thousand four hundred and eighty statute acres. The population in 1821 amounted to 289,424. ... More" [A Topographical Dictionary of England (1831) by Samuel Lewis]

Essex is a county in the East of England immediately north-east of London and is one of the home counties. It borders the counties of Suffolk and Cambridgeshire to the north, Hertfordshire to the west, Kent across the estuary of the River Thames to the south and London to the south-west. The county town is Chelmsford, which is the only city in the county. 
(https://en.wikipedia.org/wiki/Essex)

Essex used to extend all the way to Stratford but the expansion of London has lead to the south east portion being annexed by Greater London, which now extends out to approximately the M25 motorway.