Amersham is a Primary Destination in the Chilterns. Historically it was a coaching town, with a great many coaching inns. Nowadays it is a commuter town, served by the very fringes of London Underground. Amersham's position between London and the West Midlands, on one of the flatter routes through the Chilterns, has meant that several proposals to link the two areas - most notably the Northern and Western Motorway of 1923 and the High Speed 2 railway proposals of 2010 - have passed just north of the Old Town (modified proposals for HS2 take the railway south of the town to minimize damage to the historic properties).
would have passed immediately to the north of Amersham as it was then (i.e. just the southern, Old Town) 
Amersham was an important stop at the crossroads between the main coaching road between London and Aylesbury (and further to Oxford and Birmingham) and the route from Reading to Hatfield. It was mostly confined to a narrow strip of development in the Misbourne Valley (now called the Old Town), with a large common to the north. At the turn of the 20th Century, the Metropolitan railway opened at the top of the hill, and spurred some development there. However it wasn't until the Metroland movement of the 1930s that development 'on-the-hill' really took off.
The maps below show some of the history of road numbering in Amersham.
Development, or perhaps error, led to the creation in 1924 of the A4090, running along the top of the hill. The next year, the B4441 was created, properly serving the core of the new developments in the area known as "Amersham on the Hill". The 1920s South Buckinghamshire Renumbering changed the number of the Amersham to Beaconsfield road to B472, which was undone in the 1935 Road numbering revision. Also renumbered in 1935 was the A416 Amersham - High Wycombe - Marlow - A4 route and the A4090: both became parts of the A404.
Being the shortest route between Aylesbury and London, the A413 got upgraded over time, giving Amersham a controversial bypass in the 1980s. Pressure from Hertfordshire Council to upgrade the A41, led to the A413's fall from favour as the way to get to Aylesbury, but only after Buckinghamshire Council had built the controversial Amersham and Wendover bypasses.
The A404 to High Wycombe used to be primary; however, when Beaconsfield became a Primary Destination, the primary route between the two was diverted via Beaconsfield and the M40. There never has been a primary route between Watford and Amersham.
Three cycle loops from Amersham, into the surrounding areas, have been created. Each one is roughly 25 miles long, though short cuts exist to create family-friendly routes. All routes begin at the council offices near to the station.
Hampden Route (Red, North West) via Chesham Bois, Hyde Heath, Little Missenden, Holmer Green, Great Kingshill, Prestwood, Great Missenden, South Heath, Kings Ash, The Lea, Lee Common, Chartridge, Lower Pednor, Chesham and Chesham Bois