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McKinney Falls State Park

The closest serious nature park to home — a 744-acre TPWD park where Onion Creek pours over Cretaceous Edwards limestone ledges into two named falls, with a 500+ year-old bald cypress, a Tonkawa-era rockshelter on the National Register, and ~9 miles of trail, all 13 miles from downtown Austin.

McKinney Falls State Park

The closest serious nature park to home — a 744-acre TPWD park where Onion Creek pours over Cretaceous Edwards limestone ledges into two named falls, with a 500+ year-old bald cypress, a Tonkawa-era rockshelter on the National Register, and ~9 miles of trail, all 13 miles from downtown Austin.

Scope note: this template covers steps 1–3 of the adventures pipeline (identify, support Maxine's research, shape goals). The deliverable webpage

  • video at step 6 is Maxine's own work — don't scaffold it here.

Links & Maps

Official:

Maps:

Reference & background:

Must-See / Big Items

Ranked roughly by payoff.

  1. Upper Falls — Onion Creek pours over a wide limestone shelf into a deep pool used for swimming when flow is good. Best in spring; degrades to a chain of stagnant pools in late summer drought. Walk the bare-rock streambed when the creek is low — sculpted potholes, polished channels, fossiliferous Cretaceous beds.
  2. Lower Falls — taller, narrower drop downstream of the homestead ruins; the more dramatic of the two falls but harder/wetter to reach into the plunge pool. Excellent geologic exposure of stair-step Edwards limestone.
  3. Old Baldy bald cypress (Taxodium distichum) — on Onion Creek near the homestead; estimated 500+ years old, ~103 ft tall, ~16 ft circumference. One of the oldest bald cypresses on Texas public land. Hard to photograph at scale — get a person in the shot.
  4. Smith Rockshelter — a natural Edwards limestone overhang on the 0.8 mi Smith Rockshelter Trail. Used by Native Americans (Tonkawa-related groups latest) from ~500 BCE to the 18th century. On the National Register of Historic Places. Look at it as a working space, not a "cave": southern exposure, water nearby, a flat dry living surface.
  5. Homestead ruins & gristmill foundations — Thomas F. McKinney's 1850s rock house and horse-trainer's cabin between the two falls; physical evidence of the antebellum economy that briefly operated here before the Civil War wrecked it.
  6. Onion Creek Hike & Bike Trail — 2.8 mi paved loop; stroller-/road-bike-friendly; the most accessible part of the park and a fast lap for a fitness pass.
  7. Rock Shelter Trail + Williamson Creek confluence — short, takes you to where Williamson hits Onion. Good cross-section of riparian bald-cypress gallery forest.
  8. Painted bunting territory (spring) — males set up territories along edges of the campground loop; an electric-blue/red/green bird most kids think is fake when they see it.

Stretch goals (do if time allows):

  • Look for fossils in the falls bedrock — bivalves and gastropods in the Cretaceous limestone are common; nothing collectable (state park, leave-no-trace), but lots to photograph.
  • Mountain-bike the unpaved trails on a separate dawn trip.
  • Overnight in a remodeled cabin — closest serious cabin camping to home.

Research angles for Maxine

The research is hers — list questions to investigate and sources to start from, not answers. Pitch above grade level.

Hook into Maxine's current interests: (ask before finalizing — what is she into right now? bend the questions to that.)

Questions worth chasing:

  • Science: The falls bedrock is Cretaceous Edwards Group limestone. What kind of marine environment deposited it — open shelf, shallow lagoon, reef? What fossils would you predict (rudists, oysters, gastropods)? What's the mechanism by which Onion Creek cuts stair-step ledges instead of a smooth V-channel? Old Baldy is Taxodium distichum — how does a deciduous conifer breathe with its roots submerged ("knees" / pneumatophores), and why is it deciduous when most conifers aren't?
  • History: Who were the Tonkawa, and what was their relationship to this specific spot? What kind of evidence (lithics, hearths, pictographs) tells archaeologists who lived in a rockshelter and when? Who was Thomas F. McKinney, what was he trying to build here in the 1850s, and what wrecked it? How did the land get from McKinney → State Park (Smith family ownership, donation in 1970)?
  • Writing: The "falls" sometimes aren't falls — they're a dry rock channel. Write a short piece that describes the same site in two states (high flow vs. low flow) without cheating with the same adjectives.
  • Math: Estimate stream discharge at Upper Falls on the day you visit. Pick a cross-section, measure width, estimate average depth, time a floating leaf across a known distance for velocity, multiply. Compare to the USGS Onion Creek gauge if there's one upstream that day.
  • Art: The polished limestone potholes are sculptures made by water-driven pebbles spinning. Sketch one in plan view + cross-section. How would you reproduce the form in clay or carved stone?

Starting sources (not exhaustive — she'll find more):

Observable field goals

Goals Maxine can verify or document in the field at step 5 (confirm & document). Concrete things to look at, count, measure, identify, or photograph — not vague "learn about X."

  • Photograph at least one identifiable marine fossil in the falls bedrock with a coin or finger for scale; note location (which falls, which ledge).
  • Measure the diameter of Old Baldy at chest height with a soft tape; calculate circumference and approximate age using a ring-width estimate for Taxodium distichum in Central TX.
  • Count distinct limestone "steps" at Upper Falls between the lip and the plunge pool; estimate average step rise + run.
  • Photograph the entrance to Smith Rockshelter from outside, and one shot of the shelter ceiling for soot/staining evidence.
  • Identify and photograph 3 distinct trees along Onion Creek (e.g. bald cypress, pecan, sycamore, cedar elm) and one wildflower in season.
  • Estimate Onion Creek flow at the Upper Falls cross-section using the floating-leaf method (record width, average depth, velocity, computed discharge in cfs).

Suggested itinerary

Half-day (recommended first visit):

  1. 8:00 a.m. — Leave home; arrive park 8:30 a.m. (gate opens 8). Day-pass reservation already in pocket.
  2. 8:45 a.m. — Walk to Upper Falls; swim or scramble depending on flow + temperature. ~45 min.
  3. 9:45 a.m. — Down to Lower Falls and the homestead ruins. ~45 min.
  4. 10:30 a.m. — Old Baldy + walk back upstream along Onion Creek.
  5. 11:30 a.m. — Smith Rockshelter Trail (0.8 mi RT).
  6. 12:30 p.m. — Back to car. Lunch in S Austin (closer to home than fighting traffic at the park).

Full-day add-ons:

  • Onion Creek H&B Trail full lap (2.8 mi) before it gets hot.
  • Visitor Center (Noon–4 p.m. Tue–Thu, 9–4 Fri–Sun) for the park orientation exhibits.

Two-day version (camping):

  • Arrive afternoon, set up camp, evening walk to Upper Falls at golden hour. Sunset dinner at camp. Stargazing is weak (Austin glow) — don't plan astronomy here.
  • Day 2: Dawn walk for painted buntings if spring; full hike of trail network; pack out by checkout.

Family roles:

  • Chris leads: Driving, day-pass reservation, geology setup at the falls bedrock, fossil-spotting.
  • Heather leads: Bird ID along the creek (painted bunting, herons), tree ID, swim safety call at the pools.
  • Maxine drives: Stream-discharge measurement at Upper Falls; route planning between the four major stops (which order); decide whether Smith Rockshelter or the homestead ruins is more interesting to photograph.
  • Solo vs. both parents: Easy enough for either parent solo with Maxine — short distances, low commitment.

Connections

Combines well with:

  • barton-creek-greenbelt — opposite end of Austin, same Edwards limestone, very different drainage. A two-park "Austin limestone" day is doable in cool weather (one in the morning, one in the afternoon).
  • Lady Bird Johnson Wildflower Center — 15 min south, fits as an add-on if visiting in spring bloom.
  • Austin Nature & Science Center / Zilker Botanical — sibling local stops.

Feeds into home projects / future adventures:

  • Anchor for a "limestone of Central Texas" sequence: McKinney Falls (Edwards, in-city) → Hamilton Pool (collapsed grotto) → Pedernales Falls (Glen Rose stair-steps) → Inner Space Cavern (karst dissolution from below).
  • The bald-cypress angle pairs with caddo-lake (cypress swamp) and lost-maples (mixed riparian gallery with cypress and relict maples).
  • Smith Rockshelter is a natural lead-in to lower-pecos rock-art trips (Seminole Canyon SHP) and the Witte Museum's pictograph hall.

Open questions / still to research (Chris's side)

  • Check Onion Creek flow (USGS gauge or recent visitor reports) within 48 hr of any planned swim trip — the falls go from great to bone-dry fast in summer.
  • Book day pass online a week+ ahead for any weekend visit; the park does turn cars away at the gate.
  • Decide swim vs. hike focus — they actually require different gear loads.
  • If camping: walk a few campsites on a day visit first; compare loops for shade and noise from the highway.
  • Confirm whether the Visitor Center has a current exhibit on the rockshelter pictographs (some have faded — interpretation may live indoors).