Quite the little group of volunteer history buffs gathered on the south banks of Lady Bird Lake at 9 a.m. The group of nine included a retired judge, an archeologist, an archivist and — to his total delight — a young newcomer to Austin. One lives in La Grange, another in Pearland, but most of us hail from Austin.

Austin History Brain Bank: Mike Miller, Bob Ward, Phoebe Allen, Greg Walker, Bob Perkins, Doug Stienstra, Richard Denney and Lanny Ottosen. Other buffs who contributed to pre-hike digital chat: Kim McKnight, Steven Gonzalez, Bobby Cervantes, Kevin Anderson and Ted Eubanks.

We all share in common an interest in Austin history. The informal group first gathered digitally a few weeks ago when Judge Bob Perkins asked about the locations of Colorado River crossings for the Chisholm Trail, which shuttled cattle in the thousands from Texas to Kansas in the late 19th century.

On the south bank at Tinnan Ford.

A flood of data — records, photos, maps, overlaid maps — where shared in long email threads. Finally, we decided to find the most likely sites for at least Tinnan Ford, while keeping an eye on the other mapped crossings — Shoal Creek, Congress Avenue, Longhorn Dam, Stones Ford, Comanche Ferry and Montopolis Ferry.

I should take a second to point out that this blog post represents only the barest sketch of the process of nailing down these locations. We’ll return to this material in a few weeks with more rigorous fact checking.

We met at the international hostel right where Tinnan Ford Road dead-ends into Lakeshore Boulevard. After merrily checking maps and sharing references, we headed out the finger of land that leads toward Snake Island. To our right was a former gravel pit. Aerial shots told us that a large mining operation once stood here.

Comparing notes on the north bank.

Here, at an ancient cypress, we found what we believed to be the southern entry for Tinnan Ford. One could look across the lake at an angle to see where it would have picked up on Robert Martinez Street Jr. north of the river.

But why were these crossings sometimes called “fords” and at other times “ferries”? “Seasonal changes in the river’s level,” correctly chimed in Austin History Center chief archivist Mike Miller.

A fortuitous sign.

We then headed to the other side of the river, across the Longhorn Dam, which bears a historical marker about the trail. After examining several possible low spots on the bank, we settled near another old cypress and guessed this was the other end of the ford.

We still had questions: Was Stones Ford different from Tinnan Ford? Where were the downstream crossings? Below the current Longhorn Dam and Montopolis Bridge, which connect banks that are too high?

One of our party on the limestone flats at the remains of Chambers Mill Dam, just below Longhorn Dam on the Colorado River.

A few of us headed downstream to the site of the abandoned Chambers Mill Dam, located on a vast limestone ledge just below the Longhorn Dam. We easily could imagine a low-water crossing here, except that the banks above the flats were too high. A little farther downstream?

Mysteries to be solved later …