Bantu-speaking cultivators of the ridge country between Mount Kenya and the Aberdare Range, descended from the Thagicu; organised by ridge, clan and age-set rather than by kings. They cleared the highland forest southwards from Murang'a into Kiambu through the 18th and 19th centuries and traded grain and livestock with the Maasai of the plains and the Akamba to the south-east.
Not an ending: the Kikuyu are Kenya's largest people, still centred on Murang'a, Nyeri and Kiambu. The map hands off to the East Africa Protectorate declared in 1895, which covers the highlands continuously thereafter.
The standard scholarly history of the pre-colonial Kikuyu, written from oral tradition; verified via Open Library (OL3229505W, ISBN 0195723147).
The earliest full ethnography of Kikuyu country, describing its boundaries, forest clearance and the Maasai frontier; full text open on the Internet Archive.