diff --git a/cwms-data-api/src/main/java/cwms/cda/servlet/SpaErrorStatusFilter.java b/cwms-data-api/src/main/java/cwms/cda/servlet/SpaErrorStatusFilter.java
new file mode 100644
index 000000000..86bcb71ec
--- /dev/null
+++ b/cwms-data-api/src/main/java/cwms/cda/servlet/SpaErrorStatusFilter.java
@@ -0,0 +1,77 @@
+package cwms.cda.servlet;
+
+import java.io.IOException;
+import java.util.Set;
+import javax.servlet.DispatcherType;
+import javax.servlet.Filter;
+import javax.servlet.FilterChain;
+import javax.servlet.RequestDispatcher;
+import javax.servlet.ServletException;
+import javax.servlet.ServletRequest;
+import javax.servlet.ServletResponse;
+import javax.servlet.annotation.WebFilter;
+import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.HttpServletResponse;
+
+/**
+ * Converts the error dispatch used to load known client-side routes into a successful response.
+ */
+@WebFilter(urlPatterns = {"/index.html"}, dispatcherTypes = {DispatcherType.ERROR})
+public final class SpaErrorStatusFilter implements Filter {
+
+    // Keep these paths synchronized with cda-gui/src/route-paths.js.
+    private static final Set<String> SPA_ROUTES = Set.of(
+        "/data-query",
+        "/filter-expressions",
+        "/legacy-format",
+        "/location-search",
+        "/regexp",
+        "/swagger-ui",
+        "/timestamps",
+        "/user-lists"
+    );
+
+    @Override
+    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
+            throws IOException, ServletException {
+        HttpServletRequest httpRequest = (HttpServletRequest)request;
+        HttpServletResponse httpResponse = (HttpServletResponse)response;
+
+        if (isClientRoute(httpRequest)) {
+            httpResponse.setStatus(HttpServletResponse.SC_OK);
+        }
+
+        chain.doFilter(request, response);
+    }
+
+    private boolean isClientRoute(HttpServletRequest request) {
+        String method = request.getMethod();
+        if (!"GET".equalsIgnoreCase(method) && !"HEAD".equalsIgnoreCase(method)) {
+            return false;
+        }
+
+        Object errorRequestUri = request.getAttribute(RequestDispatcher.ERROR_REQUEST_URI);
+        if (!(errorRequestUri instanceof String)) {
+            return false;
+        }
+
+        String path = removeContextPath((String)errorRequestUri, request.getContextPath());
+        if (path.length() > 1 && path.endsWith("/")) {
+            path = path.substring(0, path.length() - 1);
+        }
+        return SPA_ROUTES.contains(path);
+    }
+
+    private String removeContextPath(String requestUri, String contextPath) {
+        if (contextPath == null || contextPath.isEmpty()) {
+            return requestUri;
+        }
+        if (requestUri.equals(contextPath)) {
+            return "/";
+        }
+        if (requestUri.startsWith(contextPath + "/")) {
+            return requestUri.substring(contextPath.length());
+        }
+        return requestUri;
+    }
+}
diff --git a/cwms-data-api/src/main/webapp/WEB-INF/web.xml b/cwms-data-api/src/main/webapp/WEB-INF/web.xml
index 99e5889d3..d037b4ab7 100644
--- a/cwms-data-api/src/main/webapp/WEB-INF/web.xml
+++ b/cwms-data-api/src/main/webapp/WEB-INF/web.xml
@@ -34,12 +34,12 @@
             <param-value>Authorization,Content-Type,Accept,Origin,X-Requested-With</param-value>
         </init-param>
     </filter>
-    <filter-mapping>
-        <filter-name>CorsFilter</filter-name>
-        <url-pattern>/*</url-pattern>
-    </filter-mapping>
-
-    <!-- Client Side Routing for React -->
+    <filter-mapping>
+        <filter-name>CorsFilter</filter-name>
+        <url-pattern>/*</url-pattern>
+    </filter-mapping>
+
+    <!-- Client Side Routing for React -->
     <error-page>
         <error-code>404</error-code>
         <location>/index.html</location>
diff --git a/cwms-data-api/src/test/java/cwms/cda/servlet/SpaErrorStatusFilterTest.java b/cwms-data-api/src/test/java/cwms/cda/servlet/SpaErrorStatusFilterTest.java
new file mode 100644
index 000000000..7e6b27e30
--- /dev/null
+++ b/cwms-data-api/src/test/java/cwms/cda/servlet/SpaErrorStatusFilterTest.java
@@ -0,0 +1,115 @@
+package cwms.cda.servlet;
+
+import static org.junit.jupiter.api.Assertions.assertArrayEquals;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.never;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.when;
+
+import java.io.IOException;
+import javax.servlet.DispatcherType;
+import javax.servlet.FilterChain;
+import javax.servlet.RequestDispatcher;
+import javax.servlet.ServletException;
+import javax.servlet.annotation.WebFilter;
+import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.HttpServletResponse;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.ValueSource;
+
+class SpaErrorStatusFilterTest {
+
+    private final SpaErrorStatusFilter filter = new SpaErrorStatusFilter();
+
+    @Test
+    void registersForIndexErrorDispatches() {
+        WebFilter annotation = SpaErrorStatusFilter.class.getAnnotation(WebFilter.class);
+
+        assertArrayEquals(new String[] {"/index.html"}, annotation.urlPatterns());
+        assertArrayEquals(new DispatcherType[] {DispatcherType.ERROR}, annotation.dispatcherTypes());
+    }
+
+    @ParameterizedTest
+    @ValueSource(strings = {
+        "/data-query",
+        "/filter-expressions",
+        "/legacy-format",
+        "/location-search",
+        "/regexp",
+        "/swagger-ui",
+        "/swagger-ui/",
+        "/timestamps",
+        "/user-lists"
+    })
+    void returnsOkForClientRoutes(String route) throws ServletException, IOException {
+        HttpServletRequest request = buildRequest("GET", "/cwms-data" + route);
+        HttpServletResponse response = mock(HttpServletResponse.class);
+        FilterChain chain = mock(FilterChain.class);
+
+        filter.doFilter(request, response, chain);
+
+        verify(response).setStatus(HttpServletResponse.SC_OK);
+        verify(chain).doFilter(request, response);
+    }
+
+    @Test
+    void returnsOkForHeadRequest() throws ServletException, IOException {
+        HttpServletRequest request = buildRequest("HEAD", "/cwms-data/swagger-ui");
+        HttpServletResponse response = mock(HttpServletResponse.class);
+        FilterChain chain = mock(FilterChain.class);
+
+        filter.doFilter(request, response, chain);
+
+        verify(response).setStatus(HttpServletResponse.SC_OK);
+        verify(chain).doFilter(request, response);
+    }
+
+    @Test
+    void returnsOkForAlternateContextPath() throws ServletException, IOException {
+        HttpServletRequest request = buildRequest("GET", "/spk-data/swagger-ui", "/spk-data");
+        HttpServletResponse response = mock(HttpServletResponse.class);
+        FilterChain chain = mock(FilterChain.class);
+
+        filter.doFilter(request, response, chain);
+
+        verify(response).setStatus(HttpServletResponse.SC_OK);
+        verify(chain).doFilter(request, response);
+    }
+
+    @Test
+    void preservesNotFoundStatusForUnknownRoutes() throws ServletException, IOException {
+        HttpServletRequest request = buildRequest("GET", "/cwms-data/not-a-client-route");
+        HttpServletResponse response = mock(HttpServletResponse.class);
+        FilterChain chain = mock(FilterChain.class);
+
+        filter.doFilter(request, response, chain);
+
+        verify(response, never()).setStatus(HttpServletResponse.SC_OK);
+        verify(chain).doFilter(request, response);
+    }
+
+    @Test
+    void preservesNotFoundStatusForNonPageRequests() throws ServletException, IOException {
+        HttpServletRequest request = buildRequest("POST", "/cwms-data/swagger-ui");
+        HttpServletResponse response = mock(HttpServletResponse.class);
+        FilterChain chain = mock(FilterChain.class);
+
+        filter.doFilter(request, response, chain);
+
+        verify(response, never()).setStatus(HttpServletResponse.SC_OK);
+        verify(chain).doFilter(request, response);
+    }
+
+    private HttpServletRequest buildRequest(String method, String requestUri) {
+        return buildRequest(method, requestUri, "/cwms-data");
+    }
+
+    private HttpServletRequest buildRequest(String method, String requestUri, String contextPath) {
+        HttpServletRequest request = mock(HttpServletRequest.class);
+        when(request.getMethod()).thenReturn(method);
+        when(request.getContextPath()).thenReturn(contextPath);
+        when(request.getAttribute(RequestDispatcher.ERROR_REQUEST_URI)).thenReturn(requestUri);
+        return request;
+    }
+}