The answer, like so many things in this city, comes down to a hill.

Church Street between 20th and 22nd is brutally steep — steep enough that early transit planners knew a streetcar couldn't handle the grade. So instead of running the line straight up the street, they carved out a private right-of-way that cuts through the interior of the block, skirting the worst of the incline on a more manageable path. As one local put it, "If you take a walk on Church St, from 20th St to 22nd you'll find out why."

Here's the genuinely interesting part: that private right-of-way is actually the reason the J Church still exists as a rail line at all. After World War II, Muni converted most of its streetcar lines to bus routes. But because the J had this dedicated stretch of track — impossible to replicate with a bus — it survived the purge. It was eventually the last line converted to modern light rail when the Muni Metro system launched in 1981.

As for the homes crowding the tracks? The right-of-way likely predates many of the surrounding structures. San Francisco has a long history of building right up to the edge of whatever infrastructure already exists, zoning be damned. The result is a transit corridor that feels like a model train set someone built in their garage.

It's a charming quirk, and honestly, a rare case where old infrastructure decisions actually worked out. The private right-of-way saved a transit line from bureaucratic extinction. No committee. No $50 million study. Just a hill too steep and a track too useful to tear out.

Sometimes the best government planning is the planning that just gets left alone.