The post office in the Linn County town of Prairieburg has officially closed its door. The office, which opened in July of 1972, is closing because clerk Mary Devlin is quitting after 30 years, and nobody else was interested in taking the job. About 80 customers had post office boxes in the building. Officials say Prairieburg will become a rural route. Customers will be able to buy stamps from the carrier delivering their mail.