The route enters the London Borough of Islington at Goswell Road becoming a single carriageway running north from the border of the City to Angel through a mix of offices and urban housing.
Goswell Road and St John Street were the ancient routes from the City to Islington, with St John Street being the start of the Great North Road until the General Post Office headquarters was built at St Martin's-le-Grand in 1829, whereafter stagecoaches used Aldersgate Street and Goswell Road.
The New River originally flowed down the centre of Goswell Road, but is now underground and no trace of it can be seen at the surface.
The street was reported in 1720 to be "meanly built and inhabited", containing numerous inns and brothels, and it largely remained a slum area until the rebuilding that took place after the Second World War, and in particular the  residential development that spread out from the Barbican since 1980.

At the northern end of Goswell Road, the route northwards follows a one-way section to the Angel, turning right into Islington High Street.
The southwards route from Islington High Street follows City Road for a short distance before joining Goswell Road via Wakley Street.
The earliest reference to Islington High Street is its appearance on a 1590 map of the area.
At this time, nine inns (including the Angel, which subsequently gave its name to the area), as well as housing and a public pond were shown lining the street.
The Peacock Inn, one of the nine inns, and which operated on Islington High Street from 1564 to 1962, was where Tom of Tom Brown's Schooldays stayed prior to travelling to Rugby School.
In 1716 Islington High Street came under the control of the newly formed Islington Turnpike Trust.
The Trust grew rapidly and soon had control of most major roads in the area, building a number of major road arteries through the expanding residential areas, including Caledonian Road, Euston Road, City Road and New North Road.

Upper Street, running roughly north from Islington High Street to Highbury Corner, is the main shopping street of Islington, and dates back to at least the 12th century.
Livestock herded along the Great North Road for Smithfield Market, would – when passing through what was mainly fields and farmland – pause at lairs built between Upper Street and Liverpool Road by an enterprising farmer, Richard Laycock; Laycock's lairs would be used in 1861 for the site of the Royal Agricultural Hall, and a number of pubs and shops existed along the street to serve farmers and travellers headed for Smithfield.
In the 18th century, Upper Street began to develop from an agricultural to a residential area.
Ten houses were built in 1768 (later named Hornsey Row), and a further group built immediately south of Hornsey Row in 1792.
Liverpool Road, originally called Back Road, was used as an alternative to Upper Street for the Smithfield herders, and both streets have a "high pavement" constructed to protect pedestrians from being splashed by the passing animals; in places, the pavement is approximately 1 m above the road surface.


After reaching the eight-way interchange at Highbury Corner, the A1 turns north-west as Holloway Road.
Until the 14th century the route turned off along what is now Hornsey Road – the A103 road – to go through Muswell Hill, but when that became impassable a new route along Holloway Road via Highgate was created in the 14th century.
The earliest record giving the name of the road as the Holloway dates from 1307.
The main stretch of Holloway Road runs through the site of the villages of Tollington and Stroud.
The exact time of their founding is not known, but the earliest record of them dates from 1000.
The names ceased to be used by the late 17th century but are still preserved in the local place names "Tollington Park" and "Stroud Green"; since that time, the area has been known as Holloway.
The northern point of Holloway Road is the complex interchange at Archway.
The construction of the interchange left a few buildings isolated in the centre of the roundabout, including the Archway Tavern,
The route enters the London Borough of Islington at Goswell Road becoming a single carriageway running north from the border of the City to Angel through a mix of offices and urban housing. Goswell Road and St John Street were the ancient routes from the City to Islington, with St John Street being the start of the Great North Road until the General Post Office headquarters was built at St Martin's-le-Grand in 1829, whereafter stagecoaches used Aldersgate Street and Goswell Road. The New River originally flowed down the centre of Goswell Road, but is now underground and no trace of it can be seen at the surface. The street was reported in 1720 to be "meanly built and inhabited", containing numerous inns and brothels, and it largely remained a slum area until the rebuilding that took place after the Second World War, and in particular the  residential development that spread out from the Barbican since 1980.
At the northern end of Goswell Road, the route northwards follows a one-way section to the Angel, turning right into Islington High Street. The southwards route from Islington High Street follows City Road for a short distance before joining Goswell Road via Wakley Street. The earliest reference to Islington High Street is its appearance on a 1590 map of the area. At this time, nine inns (including the Angel, which subsequently gave its name to the area), as well as housing and a public pond were shown lining the street. The Peacock Inn, one of the nine inns, and which operated on Islington High Street from 1564 to 1962, was where Tom of Tom Brown's Schooldays stayed prior to travelling to Rugby School. In 1716 Islington High Street came under the control of the newly formed Islington Turnpike Trust. The Trust grew rapidly and soon had control of most major roads in the area, building a number of major road arteries through the expanding residential areas, including Caledonian Road, Euston Road, City Road and New North Road.
Upper Street, running roughly north from Islington High Street to Highbury Corner, is the main shopping street of Islington, and dates back to at least the 12th century. Livestock herded along the Great North Road for Smithfield Market, would – when passing through what was mainly fields and farmland – pause at lairs built between Upper Street and Liverpool Road by an enterprising farmer, Richard Laycock; Laycock's lairs would be used in 1861 for the site of the Royal Agricultural Hall, and a number of pubs and shops existed along the street to serve farmers and travellers headed for Smithfield. In the 18th century, Upper Street began to develop from an agricultural to a residential area. Ten houses were built in 1768 (later named Hornsey Row), and a further group built immediately south of Hornsey Row in 1792. Liverpool Road, originally called Back Road, was used as an alternative to Upper Street for the Smithfield herders, and both streets have a "high pavement" constructed to protect pedestrians from being splashed by the passing animals; in places, the pavement is approximately 1 m above the road surface.

After reaching the eight-way interchange at Highbury Corner, the A1 turns north-west as Holloway Road. Until the 14th century the route turned off along what is now Hornsey Road – the A103 road – to go through Muswell Hill, but when that became impassable a new route along Holloway Road via Highgate was created in the 14th century. The earliest record giving the name of the road as the Holloway dates from 1307. The main stretch of Holloway Road runs through the site of the villages of Tollington and Stroud. The exact time of their founding is not known, but the earliest record of them dates from 1000. The names ceased to be used by the late 17th century but are still preserved in the local place names "Tollington Park" and "Stroud Green"; since that time, the area has been known as Holloway. The northern point of Holloway Road is the complex interchange at Archway. The construction of the interchange left a few buildings isolated in the centre of the roundabout, including the Archway Tavern,
A1 in London