A fence at Maricopa Point protects a plant about an inch tall. The closure is real, but the older park web page describing only three populations is no longer the full story. Botanists have counted plants on both rims, replaced a parking lot with habitat, and rewritten the recovery targets. The plant still needs more than a good fence.

The short version

• Sentry milk-vetch, Astragalus cremnophylax var. cremnophylax, lives only in Grand Canyon National Park and remains federally endangered in the latest FWS announcement checked here.
• It grows in shallow soil pockets in Kaibab Limestone near the canyon rim. It is easy to miss and easy to step on.
• Fencing, parking-lot removal, a greenhouse and reintroduction trials addressed the visitor-pressure problem at Maricopa Point.
• NPS counted 16,705 plants across both rims in 2016. That is a dated census, not today’s population or proof of recovery.
• FWS approved a revised recovery plan in 2025. Older online descriptions of three populations and older recovery thresholds should not be treated as current.
• The designated Maricopa Point Endangered Plant Area is closed to public presence, use and access without written superintendent permission under the June 2026 park compendium.

The plant that lives in the cracks

The sentry milk-vetch is a perennial in the pea family. NPS describes a plant about an inch high, with compound leaves of five to nine small leaflets and tiny lavender flowers. Mature mats can be only a few inches across. It is not a shrub with a dramatic silhouette. It is the sort of thing a person looking up at the canyon could flatten without ever seeing it.

Its habitat is equally specific: shallow soil lodged in cracks and pockets of Kaibab Limestone near the rim. The park says it grows within 25 feet of the edge. That is an ecological description, not a reason to go looking for individual plants. NPS identifies mason bees and hoverflies among its pollinators. Relatively few seedlings reach maturity. A patch of bare rock is not necessarily spare real estate.

The species is endemic to the park: NPS calls it the “only place in the world that this plant lives.” NPS says Marcus E. Jones reported it as “common” in 1903; roughly four decades later Rupert Barneby called it “of great rarity.” Those two descriptions tell us how the observers characterized what they saw, not how many plants occupied every mile of rim in between. The evidence for the actual management problem is more direct: FWS says human trampling at Maricopa was a major threat when the plant was federally listed as endangered in 1990.

A parking lot becomes habitat

The practical response was not simply to tell visitors to watch their feet. NPS fenced the Maricopa population in 1990. In 2008, it removed the nearby parking lot and relocated a trail away from occupied ground. Part of the former paved area was then prepared for reintroduction. This is infrastructure in reverse: remove pavement, prepare ground, and give plants room to establish.

NPS also built a passive solar greenhouse in 2009. The greenhouse provided a way to grow plants from collected seed without betting every trial on survival in the field. No natural pollinators were inside, so staff hand-pollinated flowers. In July 2011 the park planted 80 greenhouse-grown plants and 240 seeds in the restoration site. A later NPS project account says 41 of those 80 plants remained alive in 2012; it separately reports that approximately half of 255 seeds planted in 2012 germinated. These are not the same seed cohort, and neither figure says the entire species had recovered.

That distinction matters because this plant responds to conditions outside a greenhouse spreadsheet. The revised federal plan lists climate stress, invasive plants, limited genetic diversity and possible bison trampling on the North Rim as concerns to watch. It does not say that bison have already destroyed all northern populations. Conservation here is monitoring, habitat protection and adjustment, not a single heroic planting day.

Three populations? Check the date

The park’s species page still says “only three populations” and quotes a total of 2,500 wild plants in 2011. That paragraph should not be lifted into a present-day fact box. A separate NPS 2016 field report documented 9,103 plants on the South Rim and 7,602 on the North Rim, for 16,705 total. It reported 1,524 at Maricopa when reintroduced plants were included.

The 2025 FWS final recovery plan uses a more careful map of the biology: six sites, four on the South Rim and two on the North Rim, divided into smaller subsites. Those sites are not simply the old page’s “populations” with new names. Different years, survey coverage and definitions make a neat before-and-after growth percentage unsound. FWS says the one site with long-term monitoring data, Maricopa, has generally declined since 2014. A large park-wide count in 2016 and a concerning trend at one closely watched site can both be true.

The recovery yardstick changed too. An older page repeats earlier population-based recovery targets. FWS approved a final revised plan in 2025. Its downlisting criteria call for at least 12 subsites with 100 mature plants each, plus four subsites with 900 mature plants each, distributed across the two rims, and at least ten years of stable or increasing trend data at those four. Delisting calls for six subsites with at least 900 mature plants and additional monitoring and trend evidence. A recovery plan lays out criteria for considering a status change; it does not itself change the legal listing. The April 2025 FWS announcement still calls the plant endangered. No newer listing determination was verified for this page as of September 23, 2026.

What’s actually off-limits (and why)

The Grand Canyon Superintendent’s Compendium effective June 16, 2026 closes the Maricopa Point Endangered Plant Area to public presence, use and access without written permission from the superintendent, citing 36 CFR § 1.5(a)(2). Its stated reason is protection of a large sentry milk-vetch population. The rule names a designated plant area; it does not say that every nearby public overlook is closed. Do not cross a plant-area closure or treat a fence as a shortcut marker.

For a wider guide to what park closures actually mean, see what is off-limits. See also Orphan Mine. At Maricopa, the problem is smaller than a mine shaft and easier to overlook: the ground itself is rare habitat. Sometimes the park’s most consequential hidden infrastructure is the asphalt it removed and the line it asks visitors not to cross.

Sources

1. Sentry milk-vetch: endangered plant — National Park Service (older species account; 2011 count)
2. Recovering the Endangered Sentry Milk-Vetch, Methods & Preliminary Results — National Park Service
3. Recovering the Endangered Sentry Milk-Vetch, 2016 Update — National Park Service
4. Sentry Milk-vetch species profile — U.S. Fish & Wildlife Service
5. Sentry milk-vetch Revised Recovery Plan, final revision (2025) — U.S. Fish & Wildlife Service
6. Service Announces Sentry Milk-Vetch Recovery Plan (April 2025) — U.S. Fish & Wildlife Service
7. Grand Canyon National Park Superintendent's Compendium, effective June 16, 2026 — National Park Service