After the war Plaatje became a journalist, editor first
of one Tswana language newspaper at Mafeking and then of another at Kimberley.
Like other educated Africans he came out of the war optimistic that
the British would enfranchise all educated and propertied males
in the defeated Boer colonies (Transvaal and Orange Free State)
without regard to race. But in this he, and the others,
were soon sorely disappointed. The British gave a whites-only franchise
to the defeated Boers and thus conceded power to a Boer or white Afrikaner
parliamentary majority in the 1910 Union of South Africa
which brought together the two Boer colonies with Cape Colony and Natal.
Clinging to the old but diminished "colour blind" franchise of the Cape,
Plaatje remained one of the few Africans in South Africa
with a parliamentary vote.

Plaatje's aggravation with the British government can be seen
in an unpublished manuscript of 1908-09 titled "Sekgoma -- the Black Dreyfus".
In this booklet he castigated the British for denying legal rights
(specifically habeas corpus) to their African subjects
outside the Cape Colony.

Plaatje became politically active in the "native congress" movement
which represented the interests of educated and propertied Africans
all over South Africa. He was the first secretary-general
of the "South African Native National Congress", founded in 1912
(which renamed itself as the African National Congress or ANC
ten years later).

The first piece of major legislation presented to the whites-only
parliament of South Africa was the Natives' Land Act, eventually passed
in 1913, which was designed to entrench white power and property rights