The Main Line starts from Colombo and runs east and north past the rapidly developing centres of Ragama, Gampaha, Veyangoda, and Polgahawela.

The Main Line then continues its climb through tea country, connecting local market centres at Gampola, Nawalapitiya, and Hatton before reaching Nanu Oya.

The Main Line continues its ascent to the summit at Pattipola, 1,898 m (6,227 ft) above sea level, before descending past Bandarawela to Badulla.

The main reason for building a railway system in Sri Lanka (Ceylon) was to transport tea and coffee from the hill country to Colombo.

The Main Line was extended in stages with service to Kandy beginning in 1867, to Nawalapitiya in 1874, to Nanu Oya in 1885, to Bandarawela in 1894, and to Badulla in 1924.

[4][5] Sri Lanka Railways also began importing new diesel-multiple units to replace the aging rolling stock previously used on the line.

The new S12 trainsets built by China's CSR Corporation Limited in 2012 are designed to work on the steep gradients of the hill country.