Complex sentence: The Black-Allan Line is the eastern "straight-edge" portion of the border between the Australian states of New South Wales and Victoria that stretches north-west from Cape Howe on the Tasman Sea to Indi Springs, the headwaters of the Murray River.
Split into simpler sentences: The Black-Allan Line is the eastern "straight-edge" portion of the state border between the Australian states of New South Wales and Victoria. The line stretches north-west from Cape Howe on the Tasman Sea to Indi Springs, the headwaters of the Murray River.