The late Rev. Richard Neuhaus was the first person I recall referring to the Protestant “mainline” as the “oldline” that became the “sideline.” More and more, that seems to be the case. From high water marks in the mid-1960s, all of the “Seven Sisters” of the mainline (United Methodist, PCUSA, Episcopal Church, ELCA, United Church of Christ, Disciples of Christ, and American Baptists) have decline drastically. The Episcopal News Service, focusing on that denomination, has some of the gory details:

While membership in 16 of the Episcopal Church’s domestic dioceses and eight of its non-domestic ones grew in 2010, recently released data shows that overall membership has declined. The decrease is part of a trend that has seen membership decline by just more than 16 percent since 2000.

Membership in the Episcopal Church in 2010 was 2,125,012, with 1,951,907 in its domestic dioceses and 173,105 in the non-domestic dioceses, according to a report here. Membership in the church’s domestic dioceses in 2009 was 2,006,343, showing a decrease of 54,436 in 2010.

The research shows that the average Sunday attendance across the church in 2010 was 657,831 in the United States. That compares to 856,579 in 2000. Average Sunday attendance in the non-U.S. dioceses grew in 2010 to 40,049, compared to 35,572 in 2003 (the first year the report lists non-domestic ASA). The 2010 non-domestic ASA is down 4.4 percent from 2009’s total of 41,882.

Meanwhile, the other sisters are just as bad off:

The Evangelical Lutheran Church in America reports that its 2010 membership of 4,272,688 is a decrease of 270,349 from 2009. ELCA membership has declined every year since 1988 when there were 5,288,048 members. The 2010 decline of 5.95 percent is largest in those 22 years. There were 11,133 congregations in 1988 and 10,008 in 2010.

The Presbyterian Church USA reports that at the end of 2010 it had experienced a net loss of 61,047 members from 2009 (-2.9 percent) and a net loss of 97 congregations. There were 10,560 congregations and 2,016,091 members at the end of 2010. Total contributions for 2010 were $2,027,479,202, a loss of $74,516,440 (3.5 percent) over 2009. The average contribution per member in reporting congregations was $1,122.29.

The current membership reflects a net loss of 509,239 members, or about 20.2 percent, over the last 10 years, according to the PCUSA website. There were 11,178 congregations in 2000, 618 more than in 2010. Fifty-two percent of Presbyterian congregations have 100 or fewer members.

The United Methodist Church said earlier this year that its U.S. membership had declined while the number of Methodists in Africa, Europe and Asia grew from 3.5 million to 4.4 million in the five years ending in 2009. U.S. professing membership in 2009 was down 1.22 percent from 2008, to a 7.8 million members, according to data from the United Methodist Council on Finance and Administration. Overall UMC membership stood at 12 million in 2009, making it the third largest denomination in the United States behind the Roman Catholic Church and the Southern Baptist Convention.

In addition, the UCC has gone from a high of over 2 million to just over 1 million since 1960, while losing over 1700 of its original 7000+ churches. The Christian Church (Disciples of Christ) has gone from just under 2 million in 1958 to fewer than 700,000. The American Baptists have done better, but still not well, going from 1.6 million in the early 1980s to 1.3 million in 2006.

No matter how you slice it, the mainline–now sideline–churches are in steep, some might say terminal, decline. The PCUSA, ELCA, and Episcopal churches , especially, are losing not just members but whole congregations in growing numbers, as more and more local orthodox and evangelical churches decide that continued association with the heresy and apostasy that has come to dominate the upper reaches of those denominations are hurting them locally. Given the increasingly radical nature of the theological and moral agendas being pursued by national leadership, that trend will only accelerate, until each of these once-proud bodies are reduced to being little more than religious debating societies or Sunday hangouts for political activists.