Entry No. 21 — the San Antonio file — filed under: state-park
Government Canyon State Natural Area — after-dark ranger programs
Rangers run a 'Night Crawlers' invertebrate walk through 13,000 unlit acres of Hill Country canyon, hunting scorpions and moths that fluoresce neon blue-green under blacklight, plus a separate blanket-and-lawn-chair Star Party where the parking lot becomes a naked-eye planetarium — no telescope required, just genuinely dark sky this close to a major city.
The story
Most San Antonians know Government Canyon as 13,000 acres of rugged scrub oak and limestone trails on the Far West Side that quietly protect the city's drinking water aquifer by day. But when the main gates close at dusk, the park shifts into something far stranger. A few times a month, ranger-led after-dark programs unlock the unlit canyon rim, taking small groups out into a terrain completely devoid of city streetlights.
If you sign up for the 'Night Crawlers' walk, bring a cheap UV flashlight and click it on along the trail edge. Striped bark scorpions and native moths hiding in the leaf litter fluoresce bright neon blue-green under blacklight, transforming the dark brush into a field of glowing biological tripwires. On separate nights, volunteer astronomers take over the parking lot for Star Parties, turning the dark canyon basin into a naked-eye planetarium where you can trace constellations and planets overhead without needing heavy glass optics.
What it's like
Drive down Galm Road until the suburban streetlights disappear into thick dark brush. For Night Crawlers walks, wear sturdy closed-toe shoes for uneven limestone rock and bring your own UV flashlight—watching the dust around your boots burst into neon green scorpions is equal parts thrilling and unsettling. For Star Parties, toss a lawn chair, a blanket, and a red-lens flashlight into your trunk. Keep in mind that access after dark is strictly permitted only during these scheduled ranger events; you can't just wander into 13,000 unlit acres on your own after hours.
The move: Bring a UV flashlight for the Night Crawlers scorpion hunt one month, then come back for the Star Party to trace constellations over the canyon rim with volunteer astronomers pointing out planets.
- 📍 Far West Side / northwest Bexar County
- 💸 $
- ⚡ Low-key
- 🌗 Outdoors
Where: 12861 Galm Rd, San Antonio, TX 78254
Hours: Added 2026-07-20 — confirm current hours before you go.
⚠ Seasonal or scheduled — always check before you go.
Pair it with
- Analytical Scientific, Ltd. — Stop by this two-story science supply shop six miles away before your trek to pick up pocket flashlights, magnifying lenses, or field gear.
- Mystique Moon — Combine a night hunting for glowing scorpions in the brush with a pre-hike stop at this local metaphysical shop for crystals and tarot.
- Scobee Planetarium & Scanlan Observatory — Follow up an open-sky canyon Star Party with a trip to San Antonio College's full-dome planetarium and rooftop observatory.
Good to know
Where are the after-dark ranger programs held?
They take place inside Government Canyon State Natural Area at 12861 Galm Road in northwest Bexar County.
Do I need to bring a UV blacklight for the scorpion hunt?
Yes, bringing your own UV blacklight flashlight is essential for spotting the fluorescent scorpions and moths on the Night Crawlers walk.
Do I need my own telescope for the Star Party?
No. The skies over the canyon rim are dark enough for naked-eye stargazing, and volunteer astronomers often bring equipment and point out celestial objects.
Can I hike Government Canyon at night without a ranger?
No. The state natural area closes at dark, so after-hours entry is strictly limited to official ranger-led programs.
Plan a visit & invite your people →
Further reading: tpwd.texas.gov · Wikipedia
last checked: 2026-07-20