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| Event | Distance | When | Entry fee | Cap |
|---|---|---|---|---|
| 15K | 15K | Mar 21, 20278:00 AM | $75 | 300 |
| Half Marathon | Half Marathon | Mar 21, 20278:00 AM | $90 | 800 |
| 5K Run/Walk | 5K | Mar 21, 20278:15 AM | $40 | 500 |
| Virtual RunVirtual | – | Mar 21, 20278:00 AM | $50 | 150 |
Entry fees exclude processing fees. Prices and dates come from the race's registration page and refresh nightly.
Online registration closes Mar 21, 2027, unless the race fills first.
At $90, entry is about 33 percent above a typical half marathon in Michigan, which costs $67.50 right now.
A typical finisher at a half marathon in Michigan runs 2:07:11, about 9:42 a mile, based on 72 races with published results. Women typically finish in 2:14:18 and men in 1:58:17.
Sunrise on race morning is at about 7:36 AM, and the 15K starts at 8:00 AM. The start sits about 610 feet above sea level.
Fees exclude processing fees. Comparisons use current entry fees and published results from races nearby.
7800 Grays Dr, Grosse Ile, MI 48138
The pin marks the address the race lists, which is usually the start. The organizers have not shared a course map with us yet.
Aggregated from official results (Michigan Running Foundation) for 16th Annual Rock CF Rivers Half Marathon. Individual finisher names are not stored here.
At the 2026 Half Marathon, the fastest tenth finished in 1:29:35 or better, the top quarter in 1:41:43, and half the field in 1:57:09; the last tenth came in after 2:39:02.
At the 2026 5K Run/Walk, the fastest tenth finished in 24:47 or better, the top quarter in 29:35, and half the field in 35:35; the last tenth came in after 57:10.
At the 2026 15K, the fastest tenth finished in 1:11:44 or better, the top quarter in 1:22:31, and half the field in 1:36:48; the last tenth came in after 2:00:00.
| Age | Women | Men |
|---|---|---|
| Under 20 | 1:50:57 | 1:29:02 |
| 20-29 | 1:27:06 | 1:15:49 |
| 30-39 | 1:26:06 | 1:10:55 |
| 40-49 | 1:32:41 | 1:23:01 |
| 50-59 | 1:38:58 | 1:28:28 |
| 60-69 | 1:54:02 | 1:39:59 |
Groups with fewer than five finishers are left out. Awards vary by race; check the race's rules.
Where a finish time would have placed in 2026.
Up 15 percent since 2025.
All events combined, from official results.
From 2025 to 2026, the field went from 709 to 675 finishers, and the median time dropped from 1:58:10 to 1:57:09.
| Year | Finishers | Median | Fastest tenth | Winner |
|---|---|---|---|---|
| 2026 | 675 (-5%) | 1:57:09 | under 1:29:35 | 1:03:19 |
| 2025 | 709 | 1:58:10 | under 1:30:32 | 1:05:54 |
From each year's official results for the Half Marathon; virtual options are left out.
Faster than most Michigan half marathons
The fastest quarter of the 2026 half marathon field finished under 1:41:43, against 1:52:52 in a typical Michigan half marathon, so times here run 10 percent faster.
Compares the fastest quarter of each field, so walkers and first-timers do not skew it. It reflects the course and the field together: a flat course, cool weather, or a competitive crowd all make times faster.
Around March 21 the day usually runs from 31°F at dawn to 51°F in the afternoon, with measurable rain on about 32% of days. Cold snaps dip to 21°F and hot years reach 67°F.
Based on 90 days within a week of the date over the last 5 years, from historical weather for the start area. Not a forecast.
What the organizers of 16th Annual Rock CF Rivers Half Marathon cover on their registration page, in brief.
Schedule and packet pickup
Runners can pick up for others. Having QR codes handy will help things move quicker. We will email those out race week! Early Pick Up. Wednesday March 18 & Thursday March 19. Run Detroit (1948 Division St. Suite 105 Detroit, MI). Time…
Schedule and packet pickup
Schedule of Events for Rock CF Rivers Half Marathon Race Week! Packet Pick Up. Wednesday, March 18 & Thursday, March 19- RUNdetroit (1948 Division Ste. 105, Detroit, MI 48207). 10:00 am - 6:30 pm. Saturday, March 21- Grosse Ile MIDDLE…
Course
Our interactive Google Map can be found HE RE! Half Marathon. 15K Map. 5K Map. Detailed mapp of the airport area & shuttle parking!
Parking and travel
2027 Rock CF Rivers Half Marathon, 15K & 5K Parking Info. 1) Township Shuttle Lots by Grosse Ile Airport: Beginning at 6am to Grosse Ile High School. - Use the address 9801 Intrepid & enter off of Meridian Rd. only. - Please park where…
Shirt and medal
All participants will receive a race medal with their respective distance (including virtual!) as well as a race shirt. Here are some shots of this year's Rock CF Rivers Half Marathon race shirt and medal! 🤘. Don't miss out on your chance…
Organize this race? Add details or a correction
The 16th Annual Rock CF Rivers Half Marathon, 15K, and 5K is coming back to the island of Grosse Ile, Michigan on Sunday, March 21st, 2027 for all to come and help us outrun cystic fibrosis! Starting from the Grosse Ile High School, enjoy the flat-and-fast course en route to chasing a personal best, experiencing your first half marathon, or taking in the scenic views of the Detroit River with friends & family at one of Michigan's premier spring races.