By the time of the church's centennial celebration, the congregation had predominantly Mexican heritage, reflective of greater changes in the surrounding neighborhood.

The interior is modeled after the papal basilica of San Paolo fuori le mura (built between 386 AD and ca.

Entrance is through a shallow portico with eight massive grey-flecked, rose-colored polished granite columns, from there to pass through a narrow vestibule with four large recessed fonts in its back wall, and finally to enter the immense main body which has the most magnificent marble work to be found in any church in Chicago.

A stern large white-marble statue of the church's patron St. Adalbert, the evangelizer of Poland and martyr, stares down from the massive and elaborate thirty-five ton Cararra marble altar whose ten spiral pillars are capped with a dome-shaped ciborium.

The mural on the upper portion of the north wall above the sanctuary portrays on the left the wedding of Queen Jadwiga of Poland and Prince Jagiello of Lithuania and on the right the 1655 victory of Our Lady of Częstochowa when by the Virgin's intervention an army of 9,000 invading Swedes failed to take a monastery held by only 250 monks.

The predominant muted orange-red tones of the mural are repeated in the present color of the ambulatory wall and also in the ceiling coffers and panels of the clerestory.

The pews retain their period-authentic molasses-dark varnish; both their finish and their classical broken-curve top ornamentation matches that of the original confessionals in the east transept.

On the south (or entrance) end of the church rises a spectacular two-story choir loft with curving ranges of organ pipes on either side and a rose window of St. Cecilia in the center.