Why do some racetracks run clockwise and others counterclockwise?

Track direction mostly comes down to history, geography, and safety design rather than any single technical rule.

Most road/street circuits run clockwise
The majority of purpose-built road courses (F1, IndyCar road courses, most European circuits) run clockwise, simply because that's how many original tracks were laid out, often following old public roads or airfield perimeter layouts, and later designs followed convention.

There's no major performance reason for this. It's largely inherited from track history and layout logistics.

Ovals in the U.S. mostly run counterclockwise
Nearly all NASCAR and IndyCar ovals (Daytona, Indianapolis, Talladega, etc.) run counter-clockwise (left turns only).

This dates back to horse racing traditions in the U.S., where counter-clockwise racing was already the norm before cars existed. Early American oval tracks were often built on or adapted from horse racing tracks, so the convention carried over.

Running in one direction consistently also simplifies car setup. Ovals cars are often built asymmetrically, specifically optimized for constant left-hand turns, which wouldn't work if direction varied.

There are exceptions…

• Some tracks like Watkins Glen run clockwise because of their specific historical layout or land constraints.

• A few ovals occasionally reverse direction for special events. This is rare and mostly experimental/novelty, since safety systems and car setups aren't built for it.
• F1 has more clockwise tracks overall simply because most of its calendar is road/street circuits following the "inherited from historical road layouts" pattern rather than the horse-racing-derived oval convention.
• Fun fact: IndyCar drivers race at the Indianapolis Motor Speedway in both directions in the same month. The Indy GP, which is held on the IMS road course early each May, runs clockwise. Immediately after that comes the Indianapolis 500 (main image), when the series switches to the oval and runs in the traditional counterclockwise direction.