St. Thomas

About Ss. Andrew and Thomas Parish

Ss. Andrew and Thomas Parish is a single Catholic parish serving two worship sites — St. Thomas in Potosi and St. Andrew in Tennyson — in the rolling hills of Grant County in southwestern Wisconsin. It belongs to the Diocese of Madison and is part of the St. Joseph the Worker Pastorate, a cluster of seven rural churches supported by three priests and a deacon. The pastorate describes its mission as inviting parishioners, neighbors, and visitors to 'join us for Mass, the Sacraments, events, and activities at our beautiful churches and at our Catholic schools,' under the patronage of St. Joseph the Worker.

History of St. Thomas Church

St. Thomas has roots reaching back to 1836, when Father Samuel Mazzuchelli, O.P., a Dominican from Milan, arrived in the lead-mining region to serve a diverse community of Native peoples, immigrant settlers, miners, and farmers. He organized the local Catholics into St. Thomas Parish and built a log-cabin church on what is today the St. Thomas parking lot. In 1847 the parish's first resident pastor, Father James Causse, replaced that first structure with the present brick church, built for about $11,000 and designed by Mazzuchelli himself. It is the oldest continuously used Catholic church in Wisconsin.

• Parish founded: 1836 by Fr. Samuel Mazzuchelli, O.P.
• Original log cabin church site: present St. Thomas parking lot
• Current brick church built: 1847 under Fr. James Causse, first resident pastor
• Cost of original brick construction: ~$11,000
• Architect/designer: Fr. Samuel Mazzuchelli, O.P.
• Oldest continuously used Catholic church in Wisconsin

Father Samuel Mazzuchelli, O.P. — Venerable

Father Samuel Charles Mazzuchelli (1806–1864) was an Italian-born Dominican missionary who arrived in the Wisconsin lead-mining region in the 1830s and served a diverse frontier population of Native peoples, immigrants, miners, and farmers. He designed and built more than 24 churches in Wisconsin — including St. Thomas in Potosi — and also founded Sinsinawa Mound College and a community of Dominican Sisters. Pope John Paul II declared him Venerable in 1993, opening the cause for his beatification and canonization.

• Born in Milan, Italy; member of the Order of Preachers (Dominicans)
• Designed and built over 24 churches in Wisconsin
• Founded Sinsinawa Mound College (1848) and a community of Dominican Sisters
• Declared Venerable by Pope John Paul II in 1993

The 175th Anniversary (2011)

On July 17, 2011, parishioners and visitors packed the tiny rural church of St. Thomas to mark 175 years of Catholic worship on that site. Bishop Robert C. Morlino celebrated the Mass, joined by Fr. Richard Leffler (then pastor of Ss. Andrew and Thomas Parish) and 14 concelebrating priests, with Fr. Greg Ihm serving as emcee and Deacon Larry Tranel assisting. Servers, lectors, gift bearers, and the St. Thomas Choir (led by Zita Reuter) took part, with the Fr. Samuel Mazzuchelli Assembly 1202 of the Knights of Columbus serving as honor guard. A reception in the school building displayed photographs, clippings, and treasured church sacramentals including a silver aspergillum and aspersorium and a golden monstrance.

Parish Staff & Clergy

Ss. Andrew and Thomas is served by the clergy of the St. Joseph the Worker Pastorate. Fr. Stephen (Steve) Brunner serves as Parochial Administrator of the pastorate, with Fr. Mark Miller and Fr. Sudhakar Reddy Devarapu as Parochial Vicars and Deacon Roger Scholbrock as Pastoral Minister. The priests can be reached through the St. Clement parish office in Lancaster at 608-723-4990, and the Ss. Andrew & Thomas parish office at 608-763-2120 or [email protected].

• Fr. Stephen (Steve) Brunner — Parochial Administrator
• Fr. Mark Miller — Parochial Vicar
• Fr. Sudhakar Reddy Devarapu — Parochial Vicar
• Deacon Roger Scholbrock — Pastoral Minister

Mass & Worship Schedule

The Ss. Andrew and Thomas weekend Mass schedule alternates between the two worship sites: the Saturday 4:00 PM anticipated Mass is celebrated at St. Andrew in Tennyson, the Sunday 8:00 AM Mass is celebrated at St. Thomas in Potosi, and the Sunday 10:00 AM Mass is celebrated at St. Andrew in Tennyson. A weekday Mass is offered on Friday mornings at 8:15 AM at the school during the school year.

• Saturday 4:00 PM — St. Andrew, Tennyson
• Sunday 8:00 AM — St. Thomas, Potosi
• Sunday 10:00 AM — St. Andrew, Tennyson
• Friday 8:15 AM — at school during school year

Faith Formation & Religious Education

Family Faith Formation for the parish is offered through the St. Joseph the Worker Pastorate. Families gather once a month — beginning with a shared meal at 6:00 PM, followed by lessons from 6:30–7:30 PM — at rotating host sites including Ss. Andrew–Thomas, with the rest of the month spent working through materials at home as a family. Fr. Mark leads parent lessons, Fr. Sudhakar prepares 2nd graders for First Reconciliation and First Communion, and Fr. Steve teaches 7th and 8th graders using a separate curriculum. Separate registration forms and class schedules are published for Ss. Andrew–Thomas / St. Charles, St. Clement (Lancaster), and St. Mary's (Bloomington).

• Family Faith Formation (K–6), hosted once a month
• 7th & 8th Grade Faith Formation
• High School Faith Formation Program
• First Reconciliation & First Communion preparation (2025–26 dates)
• Ss. Andrew–Thomas / St. Charles Family Faith Formation Registration Form

Catholic Education in the Parish

Catholic education in the Potosi–Tennyson area dates to 1847, when St. Andrew in Tennyson opened the first Catholic school in Wisconsin. The parish school — Sts. Andrew–Thomas Catholic School — grew over more than 175 years and was recognized as the longest-running continuous Catholic school in Wisconsin. In May 2025 the school closed due to low enrollment and financial pressure (an appeal to the Diocese of Madison was denied, and nearly three-fourths of parish offerings had been going to the school). The Ss. Andrew–Thomas Foundation has since launched efforts to open Sts. Andrew–Thomas Academy, an independent Christian school partnering with Christus Vincit Academy, to continue faith-based education in the community.

• St. Andrew school, Tennyson — first Catholic school in Wisconsin (1847)
• St. Andrew High School opened 1922, closed 1962
• Sts. Andrew–Thomas Catholic School — recognized as the longest continuously operating Catholic school in Wisconsin
• School closed May 2025 after diocesan appeal was denied
• Ss. Andrew–Thomas Foundation working to open Sts. Andrew–Thomas Academy

Parish Groups & Organizations

Ss. Andrew and Thomas is supported by parish ministries including the St. Thomas Choir, which provided music at the 2011 anniversary Mass, and the Fr. Samuel Mazzuchelli Assembly 1202 of the 4th Degree Knights of Columbus, which has served as honor guard at parish celebrations. The Ss. Andrew–Thomas Foundation, formed by parishioners, has taken the lead on continuing Catholic education in the community after the parish school's closure.

• St. Thomas Choir
• Fr. Samuel Mazzuchelli Assembly 1202 — 4th Degree Knights of Columbus
• Ss. Andrew–Thomas Foundation (Angie Pierce, vice president)

Contact & Visiting

Parishioners and visitors are encouraged to call ahead for the most current Mass and event schedule. The parish office can be reached by phone at (608) 763-2120, or by email at [email protected]. The physical address of St. Thomas Church is 100 S. Main St., Potosi, WI 53820 (parish mailing address: PO Box 160, Potosi, WI 53820). The wider St. Joseph the Worker Pastorate is administered through St. Clement Church in Lancaster (608-723-4990).

• Parish office: (608) 763-2120
• Email: [email protected]
• St. Thomas Church address: 100 S. Main St., Potosi, WI 53820
• Pastorate office: 608-723-4990 (St. Clement, Lancaster)