This route starts in the east at the M8 interchange at Newbridge and the first short section had to be aligned so as to provide a route clear of proposed developments at Turnhouse Airport. A mile-long motorway spur was built from this section to the southern approaches to the Forth Road Bridge. Continuing westwards the route by-passes the ancient town of Linlithgow, where Mary Queen of Scots was born, and then joins the Polmont and Falkirk by-pass. That by-pass was the first section of this motorway to be completed and was opened by Lord Hughes in 1968. At this point the route provides good access to the developing port and industrial area of Grangemouth which lies just to the north.
The next section of the route leading to the Stirling by-pass was the last to be completed as construction was deferred during the economic problems of the mid-1970s. Completion of the M876 link from this section to the M80 was also delayed and the two lengths of motorway were not open to traffic until 1981. The M9 and M80 are linked directly at the southern end of the Stirling by-pass at the Bannockburn interchange.
The Stirling by-pass was built in two stages, the northern stage being built first. The motorway passes to the west of Stirling and ends in the north at a roundabout junction with the all-purpose dual carriageway A9 south of Dunblane. At the planning stage objections were raised by the Stirling Town Council to the proposed line of the by-pass as being too near the town. The objections were not accepted by the Secretary of State because to move the line further away would be less satisfactory and more expensive. Moreover, the Town Council had accepted the proposed line in the County Development plan not long before.
For the most part the M9 is dual two-lane motorway but dual three-lane is provided at the eastern end between Newbridge and Kirkliston. This 6 mile section of motorway provided an eastern by-pass of Glasgow linking the Glasgow-Carlisle route, M74/A74, to the Edinburgh-Glasgow route, A8/M8, and the Monkland motorway and also to the Glasgow-Stirling route, A80/M80.
| Section | Engineer | Contractor |
| Newbridge – Kirkliston and Forth Bridge Connecting Roads | W A Fairhurst | A M Carmichael & Tarmac (now Carrilion Construction) |
| Newbridge-Lathallan (Variation Order) | W A Fairhurst | Tarmac (now Carrilion Construction) |
| Linlithgow section | W A Fairhurst | Tarmac (now Carrilion Construction) |
| Polmont and Falkirk Bypass | Stirling CC | Logan |
| Longdyke - Pirnhall | Stirling CC | Balfour Beatty |
| Stirling Bypass Stage II | Stirling CC | F Drysdale and Balfour Beatty |
| Stirling Bypass Stage I | Stirling CC | Murdoch Mackenzie |
