Canadian politicians feared American expansionism which would hem Canada into the north-east corner of the continent, unable to access the rich resources of the Prairies and making it near impossible to attract new immigrants to boost the populations and drive commerce. Western expansion was now seen as a vital part of Canada's economic future. With the acquisition of Rupert's Land and the building of the railway, the Canadian government needed to address any and all Aboriginal claims to the land. To link the country meant building through Blackfoot country. The North West Mounted Police were sent to secure the land. Treaties were negotiated and signed. Promises were made. Life for the Blackfoot changed dramatically.