There are more than 30,000 post offices in the United States, but only one of them is staffed entirely by volunteers. As Fast Company reports, the nonprofit-run Assistance League Post Office has been serving customers in San Pedro, California, since 1964.

The Assistance League Post Office is one of many contract postal units around the country. Contract postal units are run privately instead of publicly, usually by a business. The post office in San Pedro is unique in that it's operated by a nonprofit organization.

More than 50 years ago, the San Pedro chapter of the Assistance League opened the post office to service its growing community, which includes the Port of Los Angeles. The location only sold stamps for decades, then expanded into a full-service post office in 1990. In addition to running the local postal service, the Assistance League of San Pedro provides low-income residents with orthodontia care, glasses, sexual assault survivor kits, and new school clothes—all resources that revenue from the post office helps pay for.

To make its charitable mission possible, the post office relies on volunteers. Post office chairman Gayle Merrick runs a staff of 17 volunteers—all retired women between the ages of 65 and 87. Their backgrounds range from medicine to education, and they commit to giving three to four days of their time to the post office each month. Many people who volunteer at the Assistance League Post Office stick around for a while; the longest-serving volunteer worked there for a quarter of a century.

The San Pedro post office closed to the public in the spring due to the COVID-19 pandemic, and its customers and volunteers are still waiting for it to return. Merrick tells Fast Company that she hopes to reopen by October 1, in time to help process local mail-in ballots for the 2020 election.

[h/t Fast Company]