Monday, both the state of Illinois and the city of Chicago will observe Casimir Pulaski Day, in honor of the Polish war hero who died in pursuit of America’s freedom.

The holiday is observed on the first Monday of March. As part of the holiday’s observance, Cook County government offices, along with libraries, will be closed.

According to Chicago Public Schools’ calendar, CPS schools will remain open Monday. Many other schools in Illinois will also be open Monday, as it is not on the Illinois State Board of Education’s list of observed holidays.

Mail is also expected to be delivered Monday, as Casimir Pulaski Day is not listed as one of the eight observed holidays by the USPS.

The Polish-born general’s name is a common sight across Chicago – from Pulaski Road to Pulaski Park and more.

In 1977, Illinois designated the first Monday in March as Casimir Pulaski Day to recognize the war hero and the contributions that Polish Americans have made to the state and nation, according to a previous news release from the state of Illinois.

It wasn’t until nine years later that Chicago’s City Council approved a resolution, which had been introduced by Mayor Harold Washington, to declare it an official holiday.

In Buffalo, New York, another city with a large population of Polish immigrants, Pulaski Day is celebrated in mid-July with an annual parade. Both locally-based holidays shouldn’t be confused with the national General Pulaski Memorial Day, which falls on Oct. 11.

This year for Casimir Pulaski Day, Chicago’s Polish Museum of America will host a celebration with officials from all levels of government as well as Polonian organizations and institutions. While members of the public won’t be able to attend in person, the program will be livestreamed online starting at 10 a.m.